diff --git a/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/ServiceApi.java b/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/ServiceApi.java
index 7fc87099bc..3a42c4d31c 100644
--- a/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/ServiceApi.java
+++ b/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/ServiceApi.java
@@ -40,5 +40,5 @@ public interface ServiceApi {
    /**
     * The operation returns a list of tenants which the current token provides access to.
     */
-   Set<Tenant> listTenants();
+   Set<? extends Tenant> listTenants();
 }
diff --git a/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/ServiceAsyncApi.java b/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/ServiceAsyncApi.java
index b32482ff45..c890d35b10 100644
--- a/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/ServiceAsyncApi.java
+++ b/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/ServiceAsyncApi.java
@@ -57,5 +57,5 @@ public interface ServiceAsyncApi {
    @Path("/tenants")
    @RequestFilters(AuthenticateRequest.class)
    @ExceptionParser(ReturnEmptySetOnNotFoundOr404.class)
-   ListenableFuture<Set<Tenant>> listTenants();
+   ListenableFuture<? extends Set<? extends Tenant>> listTenants();
 }
diff --git a/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/TenantApi.java b/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/TenantApi.java
index f4b9e5b5fa..68a0118f43 100644
--- a/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/TenantApi.java
+++ b/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/TenantApi.java
@@ -40,7 +40,7 @@ public interface TenantApi {
    /**
     * The operation returns a list of tenants which the current token provides access to.
     */
-   Set<Tenant> list();
+   Set<? extends Tenant> list();
 
    /**
     * Retrieve information about a tenant, by tenant ID
diff --git a/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/TenantAsyncApi.java b/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/TenantAsyncApi.java
index e03a38a87f..43b1ebefe9 100644
--- a/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/TenantAsyncApi.java
+++ b/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/TenantAsyncApi.java
@@ -62,7 +62,7 @@ public interface TenantAsyncApi {
    @Path("/tenants")
    @RequestFilters(AuthenticateRequest.class)
    @ExceptionParser(ReturnEmptySetOnNotFoundOr404.class)
-   ListenableFuture<Set<Tenant>> list();
+   ListenableFuture<? extends Set<? extends Tenant>> list();
 
    /** @see TenantApi#get(String) */
    @GET
@@ -71,7 +71,7 @@ public interface TenantAsyncApi {
    @Path("/tenants/{tenantId}")
    @RequestFilters(AuthenticateRequest.class)
    @ExceptionParser(ReturnNullOnNotFoundOr404.class)
-   ListenableFuture<Tenant> get(@PathParam("tenantId") String tenantId);
+   ListenableFuture<? extends Tenant> get(@PathParam("tenantId") String tenantId);
 
    /** @see TenantApi#getByName(String) */
    @GET
@@ -80,6 +80,6 @@ public interface TenantAsyncApi {
    @Path("/tenants")
    @RequestFilters(AuthenticateRequest.class)
    @ExceptionParser(ReturnNullOnNotFoundOr404.class)
-   ListenableFuture<Tenant> getByName(@QueryParam("name") String tenantName);
+   ListenableFuture<? extends Tenant> getByName(@QueryParam("name") String tenantName);
 
 }
diff --git a/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/TokenApi.java b/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/TokenApi.java
index ebd9baa17d..9b14b2a9f4 100644
--- a/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/TokenApi.java
+++ b/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/TokenApi.java
@@ -72,6 +72,6 @@ public interface TokenApi {
     *
     * @return the set of endpoints
     */
-   Set<Endpoint> listEndpointsForToken(String token);
+   Set<? extends Endpoint> listEndpointsForToken(String token);
 
 }
diff --git a/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/TokenAsyncApi.java b/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/TokenAsyncApi.java
index 3f53195649..2473400a78 100644
--- a/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/TokenAsyncApi.java
+++ b/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/TokenAsyncApi.java
@@ -64,7 +64,7 @@ public interface TokenAsyncApi {
    @Path("/tokens/{token}")
    @RequestFilters(AuthenticateRequest.class)
    @ExceptionParser(ReturnNullOnNotFoundOr404.class)
-   ListenableFuture<Token> get(@PathParam("token") String token);
+   ListenableFuture<? extends Token> get(@PathParam("token") String token);
 
    /** @see TokenApi#getUserOfToken(String) */
    @GET
@@ -73,7 +73,7 @@ public interface TokenAsyncApi {
    @Path("/tokens/{token}")
    @RequestFilters(AuthenticateRequest.class)
    @ExceptionParser(ReturnNullOnNotFoundOr404.class)
-   ListenableFuture<User> getUserOfToken(@PathParam("token") String token);
+   ListenableFuture<? extends User> getUserOfToken(@PathParam("token") String token);
 
    /** @see TokenApi#isValid(String) */
    @HEAD
@@ -89,6 +89,6 @@ public interface TokenAsyncApi {
    @Path("/tokens/{token}/endpoints")
    @RequestFilters(AuthenticateRequest.class)
    @ExceptionParser(ReturnEmptySetOnNotFoundOr404.class)
-   ListenableFuture<Set<Endpoint>> listEndpointsForToken(@PathParam("token") String token);
+   ListenableFuture<? extends Set<? extends Endpoint>> listEndpointsForToken(@PathParam("token") String token);
 
 }
diff --git a/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/UserApi.java b/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/UserApi.java
index 88ab62e9a1..619ecf0153 100644
--- a/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/UserApi.java
+++ b/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/UserApi.java
@@ -48,7 +48,7 @@ public interface UserApi {
     * 
     * @return the list of users
     */
-   Set<User> list();
+   Set<? extends User> list();
 
    /**
     * Retrieve information about a user, by user ID
@@ -73,13 +73,13 @@ public interface UserApi {
     * 
     * @return the set of Roles granted to the user
     */
-   Set<Role> listRolesOfUser(String userId);
+   Set<? extends Role> listRolesOfUser(String userId);
 
    /**
     * List the roles a user has been granted on a specific tenant
     * 
     * @return the set of roles
     */
-   Set<Role> listRolesOfUserOnTenant(String userId, String tenantId);
+   Set<? extends Role> listRolesOfUserOnTenant(String userId, String tenantId);
 
 }
diff --git a/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/UserAsyncApi.java b/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/UserAsyncApi.java
index 7e3cf607ce..d7ba6a8bcb 100644
--- a/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/UserAsyncApi.java
+++ b/apis/openstack-keystone/src/main/java/org/jclouds/openstack/keystone/v2_0/features/UserAsyncApi.java
@@ -61,7 +61,7 @@ public interface UserAsyncApi {
    @Path("/users")
    @RequestFilters(AuthenticateRequest.class)
    @ExceptionParser(ReturnEmptySetOnNotFoundOr404.class)
-   ListenableFuture<Set<User>> list();
+   ListenableFuture<? extends Set<? extends User>> list();
 
    /** @see UserApi#get(String) */
    @GET
@@ -70,7 +70,7 @@ public interface UserAsyncApi {
    @Path("/users/{userId}")
    @RequestFilters(AuthenticateRequest.class)
    @ExceptionParser(ReturnNullOnNotFoundOr404.class)
-   ListenableFuture<User> get(@PathParam("userId") String userId);
+   ListenableFuture<? extends User> get(@PathParam("userId") String userId);
    
    /** @see UserApi#getByName(String) */
    @GET
@@ -79,7 +79,7 @@ public interface UserAsyncApi {
    @Path("/users")
    @RequestFilters(AuthenticateRequest.class)
    @ExceptionParser(ReturnNullOnNotFoundOr404.class)
-   ListenableFuture<User> getByName(@QueryParam("name") String userName);
+   ListenableFuture<? extends User> getByName(@QueryParam("name") String userName);
    
    /** @see UserApi#listRolesOfUser(String) */
    @GET
@@ -88,7 +88,7 @@ public interface UserAsyncApi {
    @Path("/users/{userId}/roles")
    @RequestFilters(AuthenticateRequest.class)
    @ExceptionParser(ReturnEmptySetOnNotFoundOr404.class)
-   ListenableFuture<Set<Role>> listRolesOfUser(@PathParam("userId") String userId);
+   ListenableFuture<? extends Set<? extends Role>> listRolesOfUser(@PathParam("userId") String userId);
 
    /** @see UserApi#listRolesOfUserOnTenant(String, String) */
    @GET
@@ -97,5 +97,5 @@ public interface UserAsyncApi {
    @Path("/tenants/{tenantId}/users/{userId}/roles")
    @RequestFilters(AuthenticateRequest.class)
    @ExceptionParser(ReturnEmptySetOnNotFoundOr404.class)
-   ListenableFuture<Set<Role>> listRolesOfUserOnTenant(@PathParam("userId") String userId, @PathParam("tenantId") String tenantId);
+   ListenableFuture<? extends Set<? extends Role>> listRolesOfUserOnTenant(@PathParam("userId") String userId, @PathParam("tenantId") String tenantId);
 }
diff --git a/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/ServiceApiExpectTest.java b/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/ServiceApiExpectTest.java
index e51d72fe05..f5e63a22af 100644
--- a/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/ServiceApiExpectTest.java
+++ b/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/ServiceApiExpectTest.java
@@ -50,7 +50,7 @@ public class ServiceApiExpectTest extends BaseKeystoneRestApiExpectTest<Keystone
                HttpResponse.builder().statusCode(200)
                         .payload(payloadFromResourceWithContentType("/tenant_list.json", APPLICATION_JSON)).build())
                .getServiceApi();
-      Set<Tenant> tenants = api.listTenants();
+      Set<? extends Tenant> tenants = api.listTenants();
       assertNotNull(tenants);
       assertFalse(tenants.isEmpty());
 
diff --git a/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/ServiceApiLiveTest.java b/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/ServiceApiLiveTest.java
index 67125bf387..b12c5ae014 100644
--- a/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/ServiceApiLiveTest.java
+++ b/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/ServiceApiLiveTest.java
@@ -37,7 +37,7 @@ public class ServiceApiLiveTest extends BaseKeystoneApiLiveTest {
 
    public void testTenants() {
       ServiceApi api = keystoneContext.getApi().getServiceApi();
-      Set<Tenant> result = api.listTenants();
+      Set<? extends Tenant> result = api.listTenants();
       assertNotNull(result);
       assertFalse(result.isEmpty());
 
diff --git a/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/TenantApiExpectTest.java b/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/TenantApiExpectTest.java
index c30cd16da9..094d657221 100644
--- a/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/TenantApiExpectTest.java
+++ b/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/TenantApiExpectTest.java
@@ -56,7 +56,7 @@ public class TenantApiExpectTest extends BaseKeystoneRestApiExpectTest<KeystoneA
                HttpResponse.builder().statusCode(200).payload(
                         payloadFromResourceWithContentType("/tenant_list.json", APPLICATION_JSON)).build())
                .getTenantApi().get();
-      Set<Tenant> tenants = api.list();
+      Set<? extends Tenant> tenants = api.list();
       assertNotNull(tenants);
       assertFalse(tenants.isEmpty());
 
@@ -74,7 +74,7 @@ public class TenantApiExpectTest extends BaseKeystoneRestApiExpectTest<KeystoneA
             HttpResponse.builder().statusCode(200).payload(
                   payloadFromResourceWithContentType("/tenant_list_att.json", APPLICATION_JSON)).build())
             .getTenantApi().get();
-      Set<Tenant> tenants = api.list();
+      Set<? extends Tenant> tenants = api.list();
       assertNotNull(tenants);
       assertFalse(tenants.isEmpty());
 
diff --git a/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/TenantApiLiveTest.java b/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/TenantApiLiveTest.java
index 3411e4ebaa..8c09e41c95 100644
--- a/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/TenantApiLiveTest.java
+++ b/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/TenantApiLiveTest.java
@@ -38,7 +38,7 @@ public class TenantApiLiveTest extends BaseKeystoneApiLiveTest {
 
    public void testTenants() {
       TenantApi api = keystoneContext.getApi().getTenantApi().get();
-      Set<Tenant> result = api.list();
+      Set<? extends Tenant> result = api.list();
       assertNotNull(result);
       assertFalse(result.isEmpty());
 
diff --git a/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/TokenApiExpectTest.java b/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/TokenApiExpectTest.java
index 54f518d487..9132077d6e 100644
--- a/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/TokenApiExpectTest.java
+++ b/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/TokenApiExpectTest.java
@@ -138,7 +138,7 @@ public class TokenApiExpectTest extends BaseKeystoneRestApiExpectTest<KeystoneAp
             authenticatedGET().endpoint(endpoint + "/v2.0/tokens/XXXXXX/endpoints").build(),
             HttpResponse.builder().statusCode(200).payload(payloadFromResourceWithContentType("/user_endpoints.json", APPLICATION_JSON)).build())
             .getTokenApi().get();
-      Set<Endpoint> endpoints = api.listEndpointsForToken("XXXXXX");
+      Set<? extends Endpoint> endpoints = api.listEndpointsForToken("XXXXXX");
       
       assertEquals(endpoints, ImmutableSet.of(
             Endpoint.builder().publicURL(URI.create("https://csnode.jclouds.org/v2.0/"))
diff --git a/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/TokenApiLiveTest.java b/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/TokenApiLiveTest.java
index d4eb9cb166..7328190ef6 100644
--- a/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/TokenApiLiveTest.java
+++ b/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/TokenApiLiveTest.java
@@ -82,7 +82,7 @@ public class TokenApiLiveTest extends BaseKeystoneApiLiveTest {
    public void testTokenEndpoints() {
 
       TokenApi api = keystoneContext.getApi().getTokenApi().get();
-      Set<Endpoint> endpoints = api.listEndpointsForToken(token);
+      Set<? extends Endpoint> endpoints = api.listEndpointsForToken(token);
       assertNotNull(endpoints);
       assertFalse(endpoints.isEmpty());
 
diff --git a/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/UserApiExpectTest.java b/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/UserApiExpectTest.java
index bf828b9ac4..01eddeff07 100644
--- a/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/UserApiExpectTest.java
+++ b/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/UserApiExpectTest.java
@@ -56,7 +56,7 @@ public class UserApiExpectTest extends BaseKeystoneRestApiExpectTest<KeystoneApi
             authenticatedGET().endpoint(endpoint + "/v2.0/users").build(),
             HttpResponse.builder().statusCode(200).payload(payloadFromResourceWithContentType("/user_list.json", APPLICATION_JSON)).build())
             .getUserApi().get();
-      Set<User> users = api.list();
+      Set<? extends User> users = api.list();
       assertNotNull(users);
       assertFalse(users.isEmpty());
 
@@ -123,7 +123,7 @@ public class UserApiExpectTest extends BaseKeystoneRestApiExpectTest<KeystoneApi
             authenticatedGET().endpoint(endpoint + "/v2.0/users/3f6c1c9ba993495ead7d2eb2192e284f/roles").build(),
             HttpResponse.builder().statusCode(200).payload(payloadFromResourceWithContentType("/user_role_list.json", APPLICATION_JSON)).build())
             .getUserApi().get();
-      Set<Role> roles = api.listRolesOfUser("3f6c1c9ba993495ead7d2eb2192e284f");
+      Set<? extends Role> roles = api.listRolesOfUser("3f6c1c9ba993495ead7d2eb2192e284f");
       assertNotNull(roles);
       assertFalse(roles.isEmpty());
       assertEquals(roles, ImmutableSet.of(
@@ -154,7 +154,7 @@ public class UserApiExpectTest extends BaseKeystoneRestApiExpectTest<KeystoneApi
             authenticatedGET().endpoint(endpoint + "/v2.0/users/3f6c1c9ba993495ead7d2eb2192e284f/roles").build(),
             HttpResponse.builder().statusCode(200).payload(payloadFromResourceWithContentType("/user_tenant_role_list.json", APPLICATION_JSON)).build())
             .getUserApi().get();
-      Set<Role> roles = api.listRolesOfUser("3f6c1c9ba993495ead7d2eb2192e284f");
+      Set<? extends Role> roles = api.listRolesOfUser("3f6c1c9ba993495ead7d2eb2192e284f");
       assertNotNull(roles);
       assertFalse(roles.isEmpty());
       assertEquals(roles, ImmutableSet.of(
diff --git a/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/UserApiLiveTest.java b/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/UserApiLiveTest.java
index 6ce1f0714f..6e9759a953 100644
--- a/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/UserApiLiveTest.java
+++ b/apis/openstack-keystone/src/test/java/org/jclouds/openstack/keystone/v2_0/features/UserApiLiveTest.java
@@ -41,7 +41,7 @@ public class UserApiLiveTest extends BaseKeystoneApiLiveTest {
    public void testUsers() {
 
       UserApi api = keystoneContext.getApi().getUserApi().get();
-      Set<User> users = api.list();
+      Set<? extends User> users = api.list();
       assertNotNull(users);
       assertFalse(users.isEmpty());
       for (User user : users) {
@@ -54,12 +54,12 @@ public class UserApiLiveTest extends BaseKeystoneApiLiveTest {
    public void testUserRolesOnTenant() {
 
       UserApi api = keystoneContext.getApi().getUserApi().get();
-      Set<User> users = api.list();
-      Set<Tenant> tenants = keystoneContext.getApi().getTenantApi().get().list();
+      Set<? extends User> users = api.list();
+      Set<? extends Tenant> tenants = keystoneContext.getApi().getTenantApi().get().list();
 
       for (User user : users) {
          for (Tenant tenant : tenants) {
-            Set<Role> roles = api.listRolesOfUserOnTenant(user.getId(), tenant.getId());
+            Set<? extends Role> roles = api.listRolesOfUserOnTenant(user.getId(), tenant.getId());
             for (Role role : roles) {
                assertNotNull(role.getId());
             }
@@ -72,7 +72,7 @@ public class UserApiLiveTest extends BaseKeystoneApiLiveTest {
 
       UserApi api = keystoneContext.getApi().getUserApi().get();
       for (User user : api.list()) {
-         Set<Role> roles = api.listRolesOfUser(user.getId());
+         Set<? extends Role> roles = api.listRolesOfUser(user.getId());
          for (Role role : roles) {
             assertNotNull(role.getId());
          }
diff --git a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/NovaApi.java b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/NovaApi.java
index 7d87c7a93c..2cf173afd5 100644
--- a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/NovaApi.java
+++ b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/NovaApi.java
@@ -100,98 +100,98 @@ public interface NovaApi {
     * Provides synchronous access to Floating IP features.
     */
    @Delegate
-   Optional<FloatingIPApi> getFloatingIPExtensionForZone(
+   Optional<? extends FloatingIPApi> getFloatingIPExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides synchronous access to Security Group features.
     */
    @Delegate
-   Optional<SecurityGroupApi> getSecurityGroupExtensionForZone(
+   Optional<? extends SecurityGroupApi> getSecurityGroupExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides synchronous access to Key Pair features.
     */
    @Delegate
-   Optional<KeyPairApi> getKeyPairExtensionForZone(
+   Optional<? extends KeyPairApi> getKeyPairExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides synchronous access to Host Administration features.
     */
    @Delegate
-   Optional<HostAdministrationApi> getHostAdministrationExtensionForZone(
+   Optional<? extends HostAdministrationApi> getHostAdministrationExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides synchronous access to Simple Tenant Usage features.
     */
    @Delegate
-   Optional<SimpleTenantUsageApi> getSimpleTenantUsageExtensionForZone(
+   Optional<? extends SimpleTenantUsageApi> getSimpleTenantUsageExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides synchronous access to Volume features.
     */
    @Delegate
-   Optional<VolumeApi> getVolumeExtensionForZone(
+   Optional<? extends VolumeApi> getVolumeExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides synchronous access to Virtual Interface features.
     */
    @Delegate
-   Optional<VirtualInterfaceApi> getVirtualInterfaceExtensionForZone(
+   Optional<? extends VirtualInterfaceApi> getVirtualInterfaceExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides synchronous access to Server Extra Data features.
     */
    @Delegate
-   Optional<ServerWithSecurityGroupsApi> getServerWithSecurityGroupsExtensionForZone(
+   Optional<? extends ServerWithSecurityGroupsApi> getServerWithSecurityGroupsExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides synchronous access to Server Admin Actions features.
     */
    @Delegate
-   Optional<AdminActionsApi> getAdminActionsExtensionForZone(
+   Optional<? extends AdminActionsApi> getAdminActionsExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
  
    /**
     * Provides synchronous access to Aggregate features.
     */
    @Delegate
-   Optional<HostAggregateApi> getHostAggregateExtensionForZone(
+   Optional<? extends HostAggregateApi> getHostAggregateExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides synchronous access to Flavor extra specs features.
     */
    @Delegate
-   Optional<FlavorExtraSpecsApi> getFlavorExtraSpecsExtensionForZone(
+   Optional<? extends FlavorExtraSpecsApi> getFlavorExtraSpecsExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides synchronous access to Quota features.
     */
    @Delegate
-   Optional<QuotaApi> getQuotaExtensionForZone(
+   Optional<? extends QuotaApi> getQuotaExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides synchronous access to Quota Classes features.
     */
    @Delegate
-   Optional<QuotaClassApi> getQuotaClassExtensionForZone(
+   Optional<? extends QuotaClassApi> getQuotaClassExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides synchronous access to Volume Type features.
     */
    @Delegate
-   Optional<VolumeTypeApi> getVolumeTypeExtensionForZone(
+   Optional<? extends VolumeTypeApi> getVolumeTypeExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
 }
diff --git a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/NovaAsyncApi.java b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/NovaAsyncApi.java
index d379006d92..53b780e320 100644
--- a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/NovaAsyncApi.java
+++ b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/NovaAsyncApi.java
@@ -98,49 +98,49 @@ public interface NovaAsyncApi {
     * Provides asynchronous access to Floating IP features.
     */
    @Delegate
-   Optional<FloatingIPAsyncApi> getFloatingIPExtensionForZone(
+   Optional<? extends FloatingIPAsyncApi> getFloatingIPExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides asynchronous access to Security Group features.
     */
    @Delegate
-   Optional<SecurityGroupAsyncApi> getSecurityGroupExtensionForZone(
+   Optional<? extends SecurityGroupAsyncApi> getSecurityGroupExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides asynchronous access to Key Pair features.
     */
    @Delegate
-   Optional<KeyPairAsyncApi> getKeyPairExtensionForZone(
+   Optional<? extends KeyPairAsyncApi> getKeyPairExtensionForZone(
             @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides asynchronous access to Host Administration features.
     */
    @Delegate
-   Optional<HostAdministrationAsyncApi> getHostAdministrationExtensionForZone(
+   Optional<? extends HostAdministrationAsyncApi> getHostAdministrationExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides asynchronous access to Simple Tenant Usage features.
     */
    @Delegate
-   Optional<SimpleTenantUsageAsyncApi> getSimpleTenantUsageExtensionForZone(
+   Optional<? extends SimpleTenantUsageAsyncApi> getSimpleTenantUsageExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides asynchronous access to Volume features.
     */
    @Delegate
-   Optional<VolumeAsyncApi> getVolumeExtensionForZone(
+   Optional<? extends VolumeAsyncApi> getVolumeExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides asynchronous access to Virtual Interface features.
     */
    @Delegate
-   Optional<VirtualInterfaceAsyncApi> getVirtualInterfaceExtensionForZone(
+   Optional<? extends VirtualInterfaceAsyncApi> getVirtualInterfaceExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
 
@@ -148,49 +148,49 @@ public interface NovaAsyncApi {
     * Provides asynchronous access to Server Extra Data features.
     */
    @Delegate
-   Optional<ServerWithSecurityGroupsAsyncApi> getServerWithSecurityGroupsExtensionForZone(
+   Optional<? extends ServerWithSecurityGroupsAsyncApi> getServerWithSecurityGroupsExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides asynchronous access to Server Admin Actions features.
     */
    @Delegate
-   Optional<AdminActionsAsyncApi> getAdminActionsExtensionForZone(
+   Optional<? extends AdminActionsAsyncApi> getAdminActionsExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides asynchronous access to HostAggregate features.
     */
    @Delegate
-   Optional<HostAggregateAsyncApi> getHostAggregateExtensionForZone(
+   Optional<? extends HostAggregateAsyncApi> getHostAggregateExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides asynchronous access to Flavor extra specs features.
     */
    @Delegate
-   Optional<FlavorExtraSpecsAsyncApi> getFlavorExtraSpecsExtensionForZone(
+   Optional<? extends FlavorExtraSpecsAsyncApi> getFlavorExtraSpecsExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides asynchronous access to Quota features.
     */
    @Delegate
-   Optional<QuotaAsyncApi> getQuotaExtensionForZone(
+   Optional<? extends QuotaAsyncApi> getQuotaExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides asynchronous access to Quota Classes features.
     */
    @Delegate
-   Optional<QuotaClassAsyncApi> getQuotaClassExtensionForZone(
+   Optional<? extends QuotaClassAsyncApi> getQuotaClassExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
    /**
     * Provides asynchronous access to Volume Type features.
     */
    @Delegate
-   Optional<VolumeTypeAsyncApi> getVolumeTypeExtensionForZone(
+   Optional<? extends VolumeTypeAsyncApi> getVolumeTypeExtensionForZone(
          @EndpointParam(parser = ZoneToEndpoint.class) @Nullable String zone);
 
 }
diff --git a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/compute/NovaComputeService.java b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/compute/NovaComputeService.java
index 622644b8df..f62ef07ca2 100644
--- a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/compute/NovaComputeService.java
+++ b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/compute/NovaComputeService.java
@@ -135,7 +135,7 @@ public class NovaComputeService extends BaseComputeService {
    }
 
    private void cleanupOrphanedSecurityGroupsInZone(Set<String> groups, String zoneId) {
-      Optional<SecurityGroupApi> securityGroupApi = novaApi.getSecurityGroupExtensionForZone(zoneId);
+      Optional<? extends SecurityGroupApi> securityGroupApi = novaApi.getSecurityGroupExtensionForZone(zoneId);
       if (securityGroupApi.isPresent()) {
          for (String group : groups) {
             for (SecurityGroup securityGroup : Iterables.filter(securityGroupApi.get().listSecurityGroups(),
@@ -152,7 +152,7 @@ public class NovaComputeService extends BaseComputeService {
    }
 
    private void cleanupOrphanedKeyPairsInZone(Set<String> groups, String zoneId) {
-      Optional<KeyPairApi> keyPairApi = novaApi.getKeyPairExtensionForZone(zoneId);
+      Optional<? extends KeyPairApi> keyPairApi = novaApi.getKeyPairExtensionForZone(zoneId);
       if (keyPairApi.isPresent()) {
          for (String group : groups) {
             for (Map<String, KeyPair> view : keyPairApi.get().listKeyPairs()) {
diff --git a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/compute/functions/CreateSecurityGroupIfNeeded.java b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/compute/functions/CreateSecurityGroupIfNeeded.java
index 250aa01944..fb9aeb824f 100644
--- a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/compute/functions/CreateSecurityGroupIfNeeded.java
+++ b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/compute/functions/CreateSecurityGroupIfNeeded.java
@@ -62,7 +62,7 @@ public class CreateSecurityGroupIfNeeded implements Function<ZoneSecurityGroupNa
       checkNotNull(zoneSecurityGroupNameAndPorts, "zoneSecurityGroupNameAndPorts");
 
       String zoneId = zoneSecurityGroupNameAndPorts.getZone();
-      Optional<SecurityGroupApi> api = novaApi.getSecurityGroupExtensionForZone(zoneId);
+      Optional<? extends SecurityGroupApi> api = novaApi.getSecurityGroupExtensionForZone(zoneId);
       checkArgument(api.isPresent(), "Security groups are required, but the extension is not availablein zone %s!", zoneId);
       logger.debug(">> creating securityGroup %s", zoneSecurityGroupNameAndPorts);
       try {
diff --git a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/compute/loaders/CreateUniqueKeyPair.java b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/compute/loaders/CreateUniqueKeyPair.java
index 49ae02b57e..6454419fe9 100644
--- a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/compute/loaders/CreateUniqueKeyPair.java
+++ b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/compute/loaders/CreateUniqueKeyPair.java
@@ -59,7 +59,7 @@ public class CreateUniqueKeyPair extends CacheLoader<ZoneAndName, KeyPair> {
       String zoneId = checkNotNull(zoneAndName, "zoneAndName").getZone();
       String prefix = zoneAndName.getName();
 
-      Optional<KeyPairApi> api = novaApi.getKeyPairExtensionForZone(zoneId);
+      Optional<? extends KeyPairApi> api = novaApi.getKeyPairExtensionForZone(zoneId);
       checkArgument(api.isPresent(), "Key pairs are required, but the extension is not available in zone %s!",
             zoneId);
 
diff --git a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/compute/loaders/LoadFloatingIpsForInstance.java b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/compute/loaders/LoadFloatingIpsForInstance.java
index 146d097f6a..578d0b1927 100644
--- a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/compute/loaders/LoadFloatingIpsForInstance.java
+++ b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/compute/loaders/LoadFloatingIpsForInstance.java
@@ -51,7 +51,7 @@ public class LoadFloatingIpsForInstance extends CacheLoader<ZoneAndId, Iterable<
    @Override
    public Iterable<FloatingIP> load(final ZoneAndId key) throws Exception {
       String zone = key.getZone();
-      Optional<FloatingIPApi> ipApiOptional = api.getFloatingIPExtensionForZone(zone);
+      Optional<? extends FloatingIPApi> ipApiOptional = api.getFloatingIPExtensionForZone(zone);
       if (ipApiOptional.isPresent()) {
          return Iterables.filter(ipApiOptional.get().listFloatingIPs(),
                   new Predicate<FloatingIP>() {
diff --git a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/config/NovaRestClientModule.java b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/config/NovaRestClientModule.java
index 579b62390f..a75b52dcb8 100644
--- a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/config/NovaRestClientModule.java
+++ b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/config/NovaRestClientModule.java
@@ -129,12 +129,12 @@ public class NovaRestClientModule<S extends NovaApi, A extends NovaAsyncApi> ext
 
    @Provides
    @Singleton
-   public LoadingCache<String, Set<Extension>> provideExtensionsByZone(final Provider<NovaApi> novaApi) {
+   public LoadingCache<String, Set<? extends Extension>> provideExtensionsByZone(final Provider<NovaApi> novaApi) {
       return CacheBuilder.newBuilder().expireAfterWrite(23, TimeUnit.HOURS)
-            .build(new CacheLoader<String, Set<Extension>>() {
+            .build(new CacheLoader<String, Set<? extends Extension>>() {
 
                @Override
-               public Set<Extension> load(String key) throws Exception {
+               public Set<? extends Extension> load(String key) throws Exception {
                   return novaApi.get().getExtensionApiForZone(key).listExtensions();
                }
 
diff --git a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ExtensionApi.java b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ExtensionApi.java
index 08647ca7e9..1b5c4d73cb 100644
--- a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ExtensionApi.java
+++ b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ExtensionApi.java
@@ -42,7 +42,7 @@ public interface ExtensionApi {
     * 
     * @return all extensions
     */
-   Set<Extension> listExtensions();
+   Set<? extends Extension> listExtensions();
 
    /**
     * Extensions may also be queried individually by their unique alias.
diff --git a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ExtensionAsyncApi.java b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ExtensionAsyncApi.java
index a2207e49b9..91b012db36 100644
--- a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ExtensionAsyncApi.java
+++ b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ExtensionAsyncApi.java
@@ -59,7 +59,7 @@ public interface ExtensionAsyncApi {
    @Consumes(MediaType.APPLICATION_JSON)
    @Path("/extensions")
    @ExceptionParser(ReturnEmptySetOnNotFoundOr404.class)
-   ListenableFuture<Set<Extension>> listExtensions();
+   ListenableFuture<? extends Set<? extends Extension>> listExtensions();
 
    /**
     * @see ExtensionApi#getExtensionByAlias
@@ -69,6 +69,6 @@ public interface ExtensionAsyncApi {
    @Consumes(MediaType.APPLICATION_JSON)
    @Path("/extensions/{alias}")
    @ExceptionParser(ReturnNullOnNotFoundOr404.class)
-   ListenableFuture<Extension> getExtensionByAlias(@PathParam("alias") String id);
+   ListenableFuture<? extends Extension> getExtensionByAlias(@PathParam("alias") String id);
 
 }
diff --git a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/FlavorApi.java b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/FlavorApi.java
index 8bb523caad..5eb5cc69ed 100644
--- a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/FlavorApi.java
+++ b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/FlavorApi.java
@@ -43,7 +43,7 @@ public interface FlavorApi {
     * 
     * @return all flavors (IDs, names, links)
     */
-   Set<Resource> listFlavors();
+   Set<? extends Resource> listFlavors();
 
    /**
     * List all flavors (all details)
diff --git a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/FlavorAsyncApi.java b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/FlavorAsyncApi.java
index ac010c2eb7..632f888668 100644
--- a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/FlavorAsyncApi.java
+++ b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/FlavorAsyncApi.java
@@ -61,7 +61,7 @@ public interface FlavorAsyncApi {
    @Consumes(MediaType.APPLICATION_JSON)
    @Path("/flavors")
    @ExceptionParser(ReturnEmptySetOnNotFoundOr404.class)
-   ListenableFuture<Set<Resource>> listFlavors();
+   ListenableFuture<? extends Set<? extends Resource>> listFlavors();
 
    /**
     * @see FlavorApi#listFlavorsInDetail
diff --git a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ImageApi.java b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ImageApi.java
index dc31674d38..89fe3e38d5 100644
--- a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ImageApi.java
+++ b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ImageApi.java
@@ -43,7 +43,7 @@ public interface ImageApi {
     * 
     * @return all images (IDs, names, links)
     */
-   Set<Resource> listImages();
+   Set<? extends Resource> listImages();
 
    /**
     * List all images (all details)
diff --git a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ImageAsyncApi.java b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ImageAsyncApi.java
index 0c623d3866..40fbc949b6 100644
--- a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ImageAsyncApi.java
+++ b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ImageAsyncApi.java
@@ -59,7 +59,7 @@ public interface ImageAsyncApi {
    @Consumes(MediaType.APPLICATION_JSON)
    @Path("/images")
    @ExceptionParser(ReturnEmptySetOnNotFoundOr404.class)
-   ListenableFuture<Set<Resource>> listImages();
+   ListenableFuture<? extends Set<? extends Resource>> listImages();
 
    /**
     * @see ImageApi#listImagesInDetail
diff --git a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ServerApi.java b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ServerApi.java
index 8b476a669e..1378b18856 100644
--- a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ServerApi.java
+++ b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ServerApi.java
@@ -47,7 +47,7 @@ public interface ServerApi {
     * 
     * @return all servers (IDs, names, links)
     */
-   Set<Resource> listServers();
+   Set<? extends Resource> listServers();
 
    /**
     * List all servers (all details)
diff --git a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ServerAsyncApi.java b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ServerAsyncApi.java
index 28db18398b..c1d7a7b79b 100644
--- a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ServerAsyncApi.java
+++ b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/features/ServerAsyncApi.java
@@ -76,7 +76,7 @@ public interface ServerAsyncApi {
    @Consumes(MediaType.APPLICATION_JSON)
    @Path("/servers")
    @ExceptionParser(ReturnEmptySetOnNotFoundOr404.class)
-   ListenableFuture<Set<Resource>> listServers();
+   ListenableFuture<? extends Set<? extends Resource>> listServers();
 
    /**
     * @see ServerApi#listServersInDetail
diff --git a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/functions/PresentWhenExtensionAnnotationNamespaceEqualsAnyNamespaceInExtensionsSet.java b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/functions/PresentWhenExtensionAnnotationNamespaceEqualsAnyNamespaceInExtensionsSet.java
index 183d5c60b0..2656b978dc 100644
--- a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/functions/PresentWhenExtensionAnnotationNamespaceEqualsAnyNamespaceInExtensionsSet.java
+++ b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/functions/PresentWhenExtensionAnnotationNamespaceEqualsAnyNamespaceInExtensionsSet.java
@@ -51,7 +51,7 @@ import com.google.common.collect.Multimap;
 @Singleton
 public class PresentWhenExtensionAnnotationNamespaceEqualsAnyNamespaceInExtensionsSet implements
       ImplicitOptionalConverter {
-   private final LoadingCache<String, Set<Extension>> extensions;
+   private final LoadingCache<String, Set<? extends Extension>> extensions;
 
    @com.google.inject.Inject(optional=true)
    @Named("openstack.nova.extensions")
@@ -88,7 +88,7 @@ public class PresentWhenExtensionAnnotationNamespaceEqualsAnyNamespaceInExtensio
    
    @Inject
    public PresentWhenExtensionAnnotationNamespaceEqualsAnyNamespaceInExtensionsSet(
-         LoadingCache<String, Set<Extension>> extensions) {
+         LoadingCache<String, Set<? extends Extension>> extensions) {
       this.extensions = checkNotNull(extensions, "extensions");
    }
 
diff --git a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/predicates/FindSecurityGroupWithNameAndReturnTrue.java b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/predicates/FindSecurityGroupWithNameAndReturnTrue.java
index 0c9f6fdaa7..0c435e3c61 100644
--- a/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/predicates/FindSecurityGroupWithNameAndReturnTrue.java
+++ b/apis/openstack-nova/src/main/java/org/jclouds/openstack/nova/v2_0/predicates/FindSecurityGroupWithNameAndReturnTrue.java
@@ -62,7 +62,7 @@ public class FindSecurityGroupWithNameAndReturnTrue implements Predicate<AtomicR
       checkNotNull(securityGroupInZoneRef, "securityGroupRef");
       final ZoneAndName securityGroupInZone = checkNotNull(securityGroupInZoneRef.get(), "securityGroupInZone");
 
-      Optional<SecurityGroupApi> api = novaApi.getSecurityGroupExtensionForZone(securityGroupInZone.getZone());
+      Optional<? extends SecurityGroupApi> api = novaApi.getSecurityGroupExtensionForZone(securityGroupInZone.getZone());
       checkArgument(api.isPresent(), "Security groups are required, but the extension is not available!");
 
       logger.trace("looking for security group %s", securityGroupInZone.slashEncode());
diff --git a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/compute/loaders/CreateUniqueKeyPairTest.java b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/compute/loaders/CreateUniqueKeyPairTest.java
index 0f86851559..c2de758b67 100644
--- a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/compute/loaders/CreateUniqueKeyPairTest.java
+++ b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/compute/loaders/CreateUniqueKeyPairTest.java
@@ -52,7 +52,9 @@ public class CreateUniqueKeyPairTest {
 
       KeyPair pair = createMock(KeyPair.class);
 
-      expect(api.getKeyPairExtensionForZone("zone")).andReturn(Optional.of(keyApi)).atLeastOnce();
+      Optional optKeyApi = Optional.of(keyApi);
+      
+      expect(api.getKeyPairExtensionForZone("zone")).andReturn(optKeyApi).atLeastOnce();
 
       expect(keyApi.createKeyPair("group-1")).andReturn(pair);
 
@@ -83,7 +85,7 @@ public class CreateUniqueKeyPairTest {
 
       KeyPair pair = createMock(KeyPair.class);
 
-      expect(api.getKeyPairExtensionForZone("zone")).andReturn(Optional.of(keyApi)).atLeastOnce();
+      expect(api.getKeyPairExtensionForZone("zone")).andReturn((Optional) Optional.of(keyApi)).atLeastOnce();
 
       expect(uniqueIdSupplier.get()).andReturn("1");
       expect(keyApi.createKeyPair("group-1")).andThrow(new IllegalStateException());
diff --git a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/compute/loaders/LoadFloatingIpsForInstanceTest.java b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/compute/loaders/LoadFloatingIpsForInstanceTest.java
index 4c32a2fe71..6a7e24c2ab 100644
--- a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/compute/loaders/LoadFloatingIpsForInstanceTest.java
+++ b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/compute/loaders/LoadFloatingIpsForInstanceTest.java
@@ -46,7 +46,7 @@ public class LoadFloatingIpsForInstanceTest {
       FloatingIPApi ipApi = createMock(FloatingIPApi.class);
       FloatingIP testIp = FloatingIP.builder().id("1").ip("1.1.1.1").fixedIp("10.1.1.1").instanceId("i-blah").build();
 
-      expect(api.getFloatingIPExtensionForZone("Zone")).andReturn(Optional.of(ipApi)).atLeastOnce();
+      expect(api.getFloatingIPExtensionForZone("Zone")).andReturn((Optional) Optional.of(ipApi)).atLeastOnce();
       expect(ipApi.listFloatingIPs()).andReturn(ImmutableSet.<FloatingIP>of(testIp)).atLeastOnce();
 
       replay(api);
@@ -65,7 +65,7 @@ public class LoadFloatingIpsForInstanceTest {
       NovaApi api = createMock(NovaApi.class);
       FloatingIPApi ipApi = createMock(FloatingIPApi.class);
 
-      expect(api.getFloatingIPExtensionForZone("Zone")).andReturn(Optional.of(ipApi)).atLeastOnce();
+      expect(api.getFloatingIPExtensionForZone("Zone")).andReturn((Optional) Optional.of(ipApi)).atLeastOnce();
 
       expect(ipApi.listFloatingIPs()).andReturn(ImmutableSet.<FloatingIP>of()).atLeastOnce();
 
@@ -86,7 +86,7 @@ public class LoadFloatingIpsForInstanceTest {
       NovaApi api = createMock(NovaApi.class);
       FloatingIPApi ipApi = createMock(FloatingIPApi.class);
 
-      expect(api.getFloatingIPExtensionForZone("Zone")).andReturn(Optional.of(ipApi)).atLeastOnce();
+      expect(api.getFloatingIPExtensionForZone("Zone")).andReturn((Optional) Optional.of(ipApi)).atLeastOnce();
 
       expect(ipApi.listFloatingIPs()).andReturn(
             ImmutableSet.<FloatingIP>of(FloatingIP.builder().id("1").ip("1.1.1.1").build()))
diff --git a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/AdminActionsApiLiveTest.java b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/AdminActionsApiLiveTest.java
index f981afcb0a..803bb23e17 100644
--- a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/AdminActionsApiLiveTest.java
+++ b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/AdminActionsApiLiveTest.java
@@ -53,7 +53,7 @@ public class AdminActionsApiLiveTest extends BaseNovaApiLiveTest {
    private ImageApi imageApi;
    private ServerApi serverApi;
    private ExtensionApi extensionApi;
-   private Optional<AdminActionsApi> apiOption;
+   private Optional<? extends AdminActionsApi> apiOption;
    private String zone;
 
    private String testServerId;
diff --git a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/FlavorExtraSpecsApiLiveTest.java b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/FlavorExtraSpecsApiLiveTest.java
index 6225888117..a666aafa45 100644
--- a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/FlavorExtraSpecsApiLiveTest.java
+++ b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/FlavorExtraSpecsApiLiveTest.java
@@ -44,7 +44,7 @@ import com.google.common.collect.Maps;
 @Test(groups = "live", testName = "FlavorExtraSpecsApiLiveTest", singleThreaded = true)
 public class FlavorExtraSpecsApiLiveTest extends BaseNovaApiLiveTest {
    private FlavorApi flavorApi;
-   private Optional<FlavorExtraSpecsApi> apiOption;
+   private Optional<? extends FlavorExtraSpecsApi> apiOption;
    private String zone;
 
    private Resource testFlavor;
diff --git a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/FloatingIPApiLiveTest.java b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/FloatingIPApiLiveTest.java
index 9970056558..8940b14da6 100644
--- a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/FloatingIPApiLiveTest.java
+++ b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/FloatingIPApiLiveTest.java
@@ -48,7 +48,7 @@ public class FloatingIPApiLiveTest extends BaseNovaApiLiveTest {
    @Test
    public void testListFloatingIPs() throws Exception {
       for (String zoneId : novaContext.getApi().getConfiguredZones()) {
-         Optional<FloatingIPApi> apiOption = novaContext.getApi().getFloatingIPExtensionForZone(zoneId);
+         Optional<? extends FloatingIPApi> apiOption = novaContext.getApi().getFloatingIPExtensionForZone(zoneId);
          if (!apiOption.isPresent())
             continue;
          FloatingIPApi api = apiOption.get();
@@ -70,7 +70,7 @@ public class FloatingIPApiLiveTest extends BaseNovaApiLiveTest {
    @Test
    public void testAllocateAndDeallocateFloatingIPs() throws Exception {
       for (String zoneId : novaContext.getApi().getConfiguredZones()) {
-         Optional<FloatingIPApi> apiOption = novaContext.getApi().getFloatingIPExtensionForZone(zoneId);
+         Optional<? extends FloatingIPApi> apiOption = novaContext.getApi().getFloatingIPExtensionForZone(zoneId);
          if (!apiOption.isPresent())
             continue;
          FloatingIPApi api = apiOption.get();
@@ -101,7 +101,7 @@ public class FloatingIPApiLiveTest extends BaseNovaApiLiveTest {
    @Test
    public void testAddAndRemoveFloatingIp() throws Exception {
       for (String zoneId : novaContext.getApi().getConfiguredZones()) {
-         Optional<FloatingIPApi> apiOption = novaContext.getApi().getFloatingIPExtensionForZone(zoneId);
+         Optional<? extends FloatingIPApi> apiOption = novaContext.getApi().getFloatingIPExtensionForZone(zoneId);
          if (!apiOption.isPresent())
             continue;
          FloatingIPApi api = apiOption.get();
diff --git a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/HostAdministrationApiLiveTest.java b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/HostAdministrationApiLiveTest.java
index 6960a6f59f..88ff7b96d7 100644
--- a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/HostAdministrationApiLiveTest.java
+++ b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/HostAdministrationApiLiveTest.java
@@ -42,7 +42,7 @@ import com.google.common.collect.Iterables;
  */
 @Test(groups = "live", testName = "HostAdministrationApiLiveTest", singleThreaded = true)
 public class HostAdministrationApiLiveTest extends BaseNovaApiLiveTest {
-   private Optional<HostAdministrationApi> optApi = Optional.absent();
+   private Optional<? extends HostAdministrationApi> optApi = Optional.absent();
 
    Predicate<Host> isComputeHost = new Predicate<Host>() {
       @Override
diff --git a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/HostAggregateApiLiveTest.java b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/HostAggregateApiLiveTest.java
index c089269d47..2224da4474 100644
--- a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/HostAggregateApiLiveTest.java
+++ b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/HostAggregateApiLiveTest.java
@@ -44,8 +44,8 @@ import com.google.common.collect.Iterables;
  */
 @Test(groups = "live", testName = "AggregateApiLiveTest", singleThreaded = true)
 public class HostAggregateApiLiveTest extends BaseNovaApiLiveTest {
-   private Optional<HostAggregateApi> apiOption;
-   private Optional<HostAdministrationApi> hostAdminOption;
+   private Optional<? extends HostAggregateApi> apiOption;
+   private Optional<? extends HostAdministrationApi> hostAdminOption;
 
    private HostAggregate testAggregate;
 
diff --git a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/QuotaApiLiveTest.java b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/QuotaApiLiveTest.java
index d1a1fe7532..efd88d750d 100644
--- a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/QuotaApiLiveTest.java
+++ b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/QuotaApiLiveTest.java
@@ -36,7 +36,7 @@ import com.google.common.collect.Iterables;
  */
 @Test(groups = "live", testName = "QuotaApiLiveTest", singleThreaded = true)
 public class QuotaApiLiveTest extends BaseNovaApiLiveTest {
-   private Optional<QuotaApi> apiOption;
+   private Optional<? extends QuotaApi> apiOption;
    private String tenant;
 
    @BeforeClass(groups = {"integration", "live"})
diff --git a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/QuotaClassApiLiveTest.java b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/QuotaClassApiLiveTest.java
index 927ed4c062..d5b80da512 100644
--- a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/QuotaClassApiLiveTest.java
+++ b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/QuotaClassApiLiveTest.java
@@ -36,7 +36,7 @@ import com.google.common.collect.Iterables;
  */
 @Test(groups = "live", testName = "QuotaClassApiLiveTest", singleThreaded = true)
 public class QuotaClassApiLiveTest extends BaseNovaApiLiveTest {
-   private Optional<QuotaClassApi> apiOption;
+   private Optional<? extends QuotaClassApi> apiOption;
    private String zone;
 
    @BeforeClass(groups = {"integration", "live"})
diff --git a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/ServerWithSecurityGroupsApiLiveTest.java b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/ServerWithSecurityGroupsApiLiveTest.java
index ebbaf78b43..533ac32432 100644
--- a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/ServerWithSecurityGroupsApiLiveTest.java
+++ b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/ServerWithSecurityGroupsApiLiveTest.java
@@ -41,7 +41,7 @@ import com.google.common.collect.Iterables;
 @Test(groups = "live", testName = "ServerWithSecurityGroupsApiLiveTest", singleThreaded = true)
 public class ServerWithSecurityGroupsApiLiveTest extends BaseNovaApiLiveTest {
    private ServerApi serverApi;
-   private Optional<ServerWithSecurityGroupsApi> apiOption;
+   private Optional<? extends ServerWithSecurityGroupsApi> apiOption;
    private String zone;
 
    @BeforeGroups(groups = {"integration", "live"})
diff --git a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/SimpleTenantUsageApiLiveTest.java b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/SimpleTenantUsageApiLiveTest.java
index 72d0a08749..dfa2c66ff7 100644
--- a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/SimpleTenantUsageApiLiveTest.java
+++ b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/SimpleTenantUsageApiLiveTest.java
@@ -38,7 +38,7 @@ public class SimpleTenantUsageApiLiveTest extends BaseNovaApiLiveTest {
 
    public void testList() throws Exception {
       for (String zoneId : novaContext.getApi().getConfiguredZones()) {
-         Optional<SimpleTenantUsageApi> optApi = novaContext.getApi().getSimpleTenantUsageExtensionForZone(zoneId);
+         Optional<? extends SimpleTenantUsageApi> optApi = novaContext.getApi().getSimpleTenantUsageExtensionForZone(zoneId);
          if (optApi.isPresent() && identity.endsWith(":admin")) {
             SimpleTenantUsageApi api = optApi.get();
             Set<SimpleTenantUsage> usages = api.listTenantUsages();
diff --git a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/VirtualInterfaceApiLiveTest.java b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/VirtualInterfaceApiLiveTest.java
index 8011a0e237..1962a0f9e8 100644
--- a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/VirtualInterfaceApiLiveTest.java
+++ b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/VirtualInterfaceApiLiveTest.java
@@ -38,7 +38,7 @@ import com.google.common.collect.Iterables;
  */
 @Test(groups = "live", testName = "VirtualInterfaceApiLiveTest", singleThreaded = true)
 public class VirtualInterfaceApiLiveTest extends BaseNovaApiLiveTest {
-   private Optional<VirtualInterfaceApi> apiOption;
+   private Optional<? extends VirtualInterfaceApi> apiOption;
    private String zone;
 
 
diff --git a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/VolumeApiLiveTest.java b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/VolumeApiLiveTest.java
index 94e537041e..cbd1e52b69 100644
--- a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/VolumeApiLiveTest.java
+++ b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/VolumeApiLiveTest.java
@@ -48,7 +48,7 @@ import com.google.common.collect.Iterables;
 @Test(groups = "live", testName = "VolumeApiLiveTest", singleThreaded = true)
 public class VolumeApiLiveTest extends BaseNovaApiLiveTest {
 
-   private Optional<VolumeApi> volumeOption;
+   private Optional<? extends VolumeApi> volumeOption;
    private String zone;
 
    private Volume testVolume;
diff --git a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/VolumeTypeApiLiveTest.java b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/VolumeTypeApiLiveTest.java
index 65fbdcabf6..9270a2e901 100644
--- a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/VolumeTypeApiLiveTest.java
+++ b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/extensions/VolumeTypeApiLiveTest.java
@@ -46,7 +46,7 @@ import com.google.common.collect.Iterables;
 @Test(groups = "live", testName = "VolumeTypeApiLiveTest", singleThreaded = true)
 public class VolumeTypeApiLiveTest extends BaseNovaApiLiveTest {
 
-   private Optional<VolumeTypeApi> volumeTypeOption;
+   private Optional<? extends VolumeTypeApi> volumeTypeOption;
    private String zone;
 
    private VolumeType testVolumeType;
diff --git a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/features/ExtensionApiLiveTest.java b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/features/ExtensionApiLiveTest.java
index 67217c5ae3..60d53b0a17 100644
--- a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/features/ExtensionApiLiveTest.java
+++ b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/features/ExtensionApiLiveTest.java
@@ -44,7 +44,7 @@ public class ExtensionApiLiveTest extends BaseNovaApiLiveTest {
    public void testListExtensions() throws Exception {
       for (String zoneId : novaContext.getApi().getConfiguredZones()) {
          ExtensionApi api = novaContext.getApi().getExtensionApiForZone(zoneId);
-         Set<Extension> response = api.listExtensions();
+         Set<? extends Extension> response = api.listExtensions();
          assert null != response;
          assertTrue(response.size() >= 0);
          for (Extension extension : response) {
diff --git a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/features/FlavorApiLiveTest.java b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/features/FlavorApiLiveTest.java
index 1374911027..87cc77c60e 100644
--- a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/features/FlavorApiLiveTest.java
+++ b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/features/FlavorApiLiveTest.java
@@ -45,7 +45,7 @@ public class FlavorApiLiveTest extends BaseNovaApiLiveTest {
    public void testListFlavors() throws Exception {
       for (String zoneId : novaContext.getApi().getConfiguredZones()) {
          FlavorApi api = novaContext.getApi().getFlavorApiForZone(zoneId);
-         Set<Resource> response = api.listFlavors();
+         Set<? extends Resource> response = api.listFlavors();
          assert null != response;
          assertTrue(response.size() >= 0);
          for (Resource flavor : response) {
diff --git a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/features/ImageApiLiveTest.java b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/features/ImageApiLiveTest.java
index 80237740c3..034666503b 100644
--- a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/features/ImageApiLiveTest.java
+++ b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/features/ImageApiLiveTest.java
@@ -41,7 +41,7 @@ public class ImageApiLiveTest extends BaseNovaApiLiveTest {
    public void testListImages() throws Exception {
       for (String zoneId : novaContext.getApi().getConfiguredZones()) {
          ImageApi api = novaContext.getApi().getImageApiForZone(zoneId);
-         Set<Resource> response = api.listImages();
+         Set<? extends Resource> response = api.listImages();
          assertNotNull(response);
          assertTrue(response.size() >= 0);
          for (Resource image : response) {
diff --git a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/features/ServerApiLiveTest.java b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/features/ServerApiLiveTest.java
index 1a02473c52..f15604d8ee 100644
--- a/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/features/ServerApiLiveTest.java
+++ b/apis/openstack-nova/src/test/java/org/jclouds/openstack/nova/v2_0/features/ServerApiLiveTest.java
@@ -40,7 +40,7 @@ public class ServerApiLiveTest extends BaseNovaApiLiveTest {
    public void testListServersInDetail() throws Exception {
       for (String zoneId : novaContext.getApi().getConfiguredZones()) {
          ServerApi api = novaContext.getApi().getServerApiForZone(zoneId);
-         Set<Resource> response = api.listServers();
+         Set<? extends Resource> response = api.listServers();
          assert null != response;
          assertTrue(response.size() >= 0);
          for (Resource server : response) {
diff --git a/core/src/main/java/org/jclouds/util/Optionals2.java b/core/src/main/java/org/jclouds/util/Optionals2.java
index 2ec4b1efc8..591c2dfb1d 100644
--- a/core/src/main/java/org/jclouds/util/Optionals2.java
+++ b/core/src/main/java/org/jclouds/util/Optionals2.java
@@ -20,6 +20,8 @@ package org.jclouds.util;
 
 import java.lang.reflect.Method;
 import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+import java.lang.reflect.WildcardType;
 
 import com.google.common.base.Optional;
 
@@ -35,7 +37,11 @@ public class Optionals2 {
       if (optional) {
          ParameterizedType futureType = ParameterizedType.class.cast(method.getGenericReturnType());
          // TODO: error checking in case this is a type, not a class.
-         syncClass = Class.class.cast(futureType.getActualTypeArguments()[0]);
+         Type t = futureType.getActualTypeArguments()[0];
+         if (t instanceof WildcardType) {
+            t = ((WildcardType) t).getUpperBounds()[0];
+         }
+         syncClass = Class.class.cast(t);
       } else {
          syncClass = method.getReturnType();
       }
diff --git a/labs/openstack-glance/src/main/java/org/jclouds/openstack/glance/v1_0/features/ImageApi.java b/labs/openstack-glance/src/main/java/org/jclouds/openstack/glance/v1_0/features/ImageApi.java
index c86757a51d..b24e368359 100644
--- a/labs/openstack-glance/src/main/java/org/jclouds/openstack/glance/v1_0/features/ImageApi.java
+++ b/labs/openstack-glance/src/main/java/org/jclouds/openstack/glance/v1_0/features/ImageApi.java
@@ -44,12 +44,12 @@ public interface ImageApi {
    /**
     * Returns a set of brief metadata about images
     */
-   Set<Image> list(ListImageOptions... options);
+   Set<? extends Image> list(ListImageOptions... options);
 
    /**
     * Returns a set of detailed metadata about images
     */
-   Set<ImageDetails> listInDetail(ListImageOptions... options);
+   Set<? extends ImageDetails> listInDetail(ListImageOptions... options);
 
    /**
     * Return metadata about an image with id
diff --git a/labs/openstack-glance/src/main/java/org/jclouds/openstack/glance/v1_0/features/ImageAsyncApi.java b/labs/openstack-glance/src/main/java/org/jclouds/openstack/glance/v1_0/features/ImageAsyncApi.java
index b7c467aa0a..c4b41caf2c 100644
--- a/labs/openstack-glance/src/main/java/org/jclouds/openstack/glance/v1_0/features/ImageAsyncApi.java
+++ b/labs/openstack-glance/src/main/java/org/jclouds/openstack/glance/v1_0/features/ImageAsyncApi.java
@@ -73,7 +73,7 @@ public interface ImageAsyncApi {
    @Consumes(MediaType.APPLICATION_JSON)
    @Path("/images")
    @ExceptionParser(ReturnEmptySetOnNotFoundOr404.class)
-   ListenableFuture<Set<Image>> list(ListImageOptions... options);
+   ListenableFuture<? extends Set<? extends Image>> list(ListImageOptions... options);
    
    /**
     * @see ImageApi#listInDetail
@@ -83,7 +83,7 @@ public interface ImageAsyncApi {
    @Consumes(MediaType.APPLICATION_JSON)
    @Path("/images/detail")
    @ExceptionParser(ReturnEmptySetOnNotFoundOr404.class)
-   ListenableFuture<Set<ImageDetails>> listInDetail(ListImageOptions... options);
+   ListenableFuture<? extends Set<? extends ImageDetails>> listInDetail(ListImageOptions... options);
    
    /**
     * @see ImageApi#show
@@ -110,7 +110,7 @@ public interface ImageAsyncApi {
    @Produces(MediaType.APPLICATION_OCTET_STREAM)
    @SelectJson("image")
    @Consumes(MediaType.APPLICATION_JSON)
-   ListenableFuture<ImageDetails> create(@HeaderParam("x-image-meta-name") String name, Payload payload, CreateImageOptions... options);
+   ListenableFuture<? extends ImageDetails> create(@HeaderParam("x-image-meta-name") String name, Payload payload, CreateImageOptions... options);
 
    /**
     * @see ImageApi#reserve
@@ -119,7 +119,7 @@ public interface ImageAsyncApi {
    @Path("/images")
    @SelectJson("image")
    @Consumes(MediaType.APPLICATION_JSON)
-   ListenableFuture<ImageDetails> reserve(@HeaderParam("x-image-meta-name") String name, CreateImageOptions... options);
+   ListenableFuture<? extends ImageDetails> reserve(@HeaderParam("x-image-meta-name") String name, CreateImageOptions... options);
 
    /**
     * @see ImageApi#upload
@@ -129,7 +129,7 @@ public interface ImageAsyncApi {
    @Produces(MediaType.APPLICATION_OCTET_STREAM)
    @SelectJson("image")
    @Consumes(MediaType.APPLICATION_JSON)
-   ListenableFuture<ImageDetails> upload(@PathParam("id") String id, Payload imageData, UpdateImageOptions... options);
+   ListenableFuture<? extends ImageDetails> upload(@PathParam("id") String id, Payload imageData, UpdateImageOptions... options);
 
    /**
     * @see ImageApi#update
@@ -138,7 +138,7 @@ public interface ImageAsyncApi {
    @Path("/images/{id}")
    @SelectJson("image")
    @Consumes(MediaType.APPLICATION_JSON)
-   ListenableFuture<ImageDetails> update(@PathParam("id") String id, UpdateImageOptions... options);
+   ListenableFuture<? extends ImageDetails> update(@PathParam("id") String id, UpdateImageOptions... options);
 
    /**
     * @see ImageApi#delete
diff --git a/labs/openstack-glance/src/main/java/org/jclouds/openstack/glance/v1_0/functions/ParseImageDetailsFromHeaders.java b/labs/openstack-glance/src/main/java/org/jclouds/openstack/glance/v1_0/functions/ParseImageDetailsFromHeaders.java
index 44ecc33d51..9bcb4e4deb 100644
--- a/labs/openstack-glance/src/main/java/org/jclouds/openstack/glance/v1_0/functions/ParseImageDetailsFromHeaders.java
+++ b/labs/openstack-glance/src/main/java/org/jclouds/openstack/glance/v1_0/functions/ParseImageDetailsFromHeaders.java
@@ -18,7 +18,21 @@
  */
 package org.jclouds.openstack.glance.v1_0.functions;
 
-import static org.jclouds.openstack.glance.v1_0.options.ImageField.*;
+import static org.jclouds.openstack.glance.v1_0.options.ImageField.CHECKSUM;
+import static org.jclouds.openstack.glance.v1_0.options.ImageField.CONTAINER_FORMAT;
+import static org.jclouds.openstack.glance.v1_0.options.ImageField.CREATED_AT;
+import static org.jclouds.openstack.glance.v1_0.options.ImageField.DELETED_AT;
+import static org.jclouds.openstack.glance.v1_0.options.ImageField.DISK_FORMAT;
+import static org.jclouds.openstack.glance.v1_0.options.ImageField.ID;
+import static org.jclouds.openstack.glance.v1_0.options.ImageField.IS_PUBLIC;
+import static org.jclouds.openstack.glance.v1_0.options.ImageField.LOCATION;
+import static org.jclouds.openstack.glance.v1_0.options.ImageField.MIN_DISK;
+import static org.jclouds.openstack.glance.v1_0.options.ImageField.MIN_RAM;
+import static org.jclouds.openstack.glance.v1_0.options.ImageField.NAME;
+import static org.jclouds.openstack.glance.v1_0.options.ImageField.OWNER;
+import static org.jclouds.openstack.glance.v1_0.options.ImageField.SIZE;
+import static org.jclouds.openstack.glance.v1_0.options.ImageField.STATUS;
+import static org.jclouds.openstack.glance.v1_0.options.ImageField.UPDATED_AT;
 
 import javax.inject.Inject;
 
@@ -44,6 +58,7 @@ public class ParseImageDetailsFromHeaders implements Function<HttpResponse, Imag
       this.dateService = dateService;
    }
 
+   @Override
    public ImageDetails apply(HttpResponse from) {
       ImageDetails.Builder<?> builder = ImageDetails.builder()
                 .id(from.getFirstHeaderOrNull(ID.asHeader()))
diff --git a/labs/openstack-glance/src/test/java/org/jclouds/openstack/glance/v1_0/features/ImageApiLiveTest.java b/labs/openstack-glance/src/test/java/org/jclouds/openstack/glance/v1_0/features/ImageApiLiveTest.java
index 6be9b4a1a0..ef457545fb 100644
--- a/labs/openstack-glance/src/test/java/org/jclouds/openstack/glance/v1_0/features/ImageApiLiveTest.java
+++ b/labs/openstack-glance/src/test/java/org/jclouds/openstack/glance/v1_0/features/ImageApiLiveTest.java
@@ -49,7 +49,7 @@ public class ImageApiLiveTest extends BaseGlanceApiLiveTest {
    public void testList() throws Exception {
       for (String zoneId : glanceContext.getApi().getConfiguredRegions()) {
          ImageApi api = glanceContext.getApi().getImageApiForRegion(zoneId);
-         Set<Image> response = api.list(ListImageOptions.Builder.limit(100));
+         Set<? extends Image> response = api.list(ListImageOptions.Builder.limit(100));
          assert null != response;
          for (Image image : response) {
             checkImage(image);
@@ -67,7 +67,7 @@ public class ImageApiLiveTest extends BaseGlanceApiLiveTest {
    public void testListInDetail() throws Exception {
       for (String zoneId : glanceContext.getApi().getConfiguredRegions()) {
          ImageApi api = glanceContext.getApi().getImageApiForRegion(zoneId);
-         Set<ImageDetails> response = api.listInDetail();
+         Set<? extends ImageDetails> response = api.listInDetail();
          assert null != response;
          for (ImageDetails image : response) {
             checkImage(image);
diff --git a/labs/openstack-quantum/src/main/java/org/jclouds/openstack/quantum/v1_0/features/NetworkApi.java b/labs/openstack-quantum/src/main/java/org/jclouds/openstack/quantum/v1_0/features/NetworkApi.java
index bd970fccc8..116a23eef7 100644
--- a/labs/openstack-quantum/src/main/java/org/jclouds/openstack/quantum/v1_0/features/NetworkApi.java
+++ b/labs/openstack-quantum/src/main/java/org/jclouds/openstack/quantum/v1_0/features/NetworkApi.java
@@ -44,12 +44,12 @@ public interface NetworkApi {
     * Returns the list of all networks currently defined in Quantum for the current tenant. The list provides the unique
     * identifier of each network configured for the tenant.
     */
-   Set<Reference> listReferences();
+   Set<? extends Reference> listReferences();
 
    /**
     * Returns all networks currently defined in Quantum for the current tenant.
     */
-   Set<Network> list();
+   Set<? extends Network> list();
 
    /**
     * Returns the specific network.
diff --git a/labs/openstack-quantum/src/main/java/org/jclouds/openstack/quantum/v1_0/features/NetworkAsyncApi.java b/labs/openstack-quantum/src/main/java/org/jclouds/openstack/quantum/v1_0/features/NetworkAsyncApi.java
index 44a8feabe9..ffb680528c 100644
--- a/labs/openstack-quantum/src/main/java/org/jclouds/openstack/quantum/v1_0/features/NetworkAsyncApi.java
+++ b/labs/openstack-quantum/src/main/java/org/jclouds/openstack/quantum/v1_0/features/NetworkAsyncApi.java
@@ -64,7 +64,7 @@ public interface NetworkAsyncApi {
    @GET
    @SelectJson("networks")
    @ExceptionParser(ReturnEmptySetOnNotFoundOr404.class)
-   ListenableFuture<Set<Reference>> listReferences();
+   ListenableFuture<? extends Set<? extends Reference>> listReferences();
 
    /**
     * @see NetworkApi#list
@@ -73,7 +73,7 @@ public interface NetworkAsyncApi {
    @SelectJson("networks")
    @Path("/detail")
    @ExceptionParser(ReturnEmptySetOnNotFoundOr404.class)
-   ListenableFuture<Set<Network>> list();
+   ListenableFuture<? extends Set<? extends Network>> list();
 
    /**
     * @see NetworkApi#get
@@ -82,7 +82,7 @@ public interface NetworkAsyncApi {
    @SelectJson("network")
    @Path("/{id}")
    @ExceptionParser(ReturnNullOnNotFoundOr404.class)
-   ListenableFuture<Network> get(@PathParam("id") String id);
+   ListenableFuture<? extends Network> get(@PathParam("id") String id);
 
    /**
     * @see NetworkApi#getDetails
@@ -91,7 +91,7 @@ public interface NetworkAsyncApi {
    @SelectJson("network")
    @Path("/{id}/detail")
    @ExceptionParser(ReturnNullOnNotFoundOr404.class)
-   ListenableFuture<NetworkDetails> getDetails(@PathParam("id") String id);
+   ListenableFuture<? extends NetworkDetails> getDetails(@PathParam("id") String id);
 
    /**
     * @see NetworkApi#create
@@ -100,7 +100,7 @@ public interface NetworkAsyncApi {
    @SelectJson("network")
    @Produces(MediaType.APPLICATION_JSON)
    @WrapWith("network")
-   ListenableFuture<Reference> create(@PayloadParam("name") String name);
+   ListenableFuture<? extends Reference> create(@PayloadParam("name") String name);
 
    /**
     * @see NetworkApi#rename
diff --git a/labs/openstack-quantum/src/main/java/org/jclouds/openstack/quantum/v1_0/features/PortApi.java b/labs/openstack-quantum/src/main/java/org/jclouds/openstack/quantum/v1_0/features/PortApi.java
index 5acc661add..5f65506caf 100644
--- a/labs/openstack-quantum/src/main/java/org/jclouds/openstack/quantum/v1_0/features/PortApi.java
+++ b/labs/openstack-quantum/src/main/java/org/jclouds/openstack/quantum/v1_0/features/PortApi.java
@@ -44,12 +44,12 @@ public interface PortApi {
    /**
     * Returns the list of all ports currently defined in Quantum for the requested network
     */
-   Set<Reference> listReferences();
+   Set<? extends Reference> listReferences();
 
    /**
     * Returns the set of ports currently defined in Quantum for the requested network.
     */
-   Set<Port> list();
+   Set<? extends Port> list();
 
    /**
     * Returns a specific port.
diff --git a/labs/openstack-quantum/src/main/java/org/jclouds/openstack/quantum/v1_0/features/PortAsyncApi.java b/labs/openstack-quantum/src/main/java/org/jclouds/openstack/quantum/v1_0/features/PortAsyncApi.java
index c0c1e44b3c..a11b474b1d 100644
--- a/labs/openstack-quantum/src/main/java/org/jclouds/openstack/quantum/v1_0/features/PortAsyncApi.java
+++ b/labs/openstack-quantum/src/main/java/org/jclouds/openstack/quantum/v1_0/features/PortAsyncApi.java
@@ -64,7 +64,7 @@ public interface PortAsyncApi {
    @GET
    @SelectJson("ports")
    @ExceptionParser(ReturnEmptySetOnNotFoundOr404.class)
-   ListenableFuture<Set<Reference>> listReferences();
+   ListenableFuture<? extends Set<? extends Reference>> listReferences();
 
    /**
     * @see PortApi#list
@@ -73,7 +73,7 @@ public interface PortAsyncApi {
    @SelectJson("ports")
    @Path("/detail")
    @ExceptionParser(ReturnEmptySetOnNotFoundOr404.class)
-   ListenableFuture<Set<Port>> list();
+   ListenableFuture<? extends Set<? extends Port>> list();
 
    /**
     * @see PortApi#get
@@ -82,7 +82,7 @@ public interface PortAsyncApi {
    @SelectJson("port")
    @Path("/{id}")
    @ExceptionParser(ReturnNullOnNotFoundOr404.class)
-   ListenableFuture<Port> get(@PathParam("id") String id);
+   ListenableFuture<? extends Port> get(@PathParam("id") String id);
 
    /**
     * @see PortApi#getDetails
@@ -92,14 +92,14 @@ public interface PortAsyncApi {
    @Consumes(MediaType.APPLICATION_JSON)
    @Path("/{id}/detail")
    @ExceptionParser(ReturnNullOnNotFoundOr404.class)
-   ListenableFuture<PortDetails> getDetails(@PathParam("id") String id);
+   ListenableFuture<? extends PortDetails> getDetails(@PathParam("id") String id);
 
    /**
     * @see PortApi#create()
     */
    @POST
    @SelectJson("port")
-   ListenableFuture<Reference> create();
+   ListenableFuture<? extends Reference> create();
 
    /**
     * @see PortApi#create(org.jclouds.openstack.quantum.v1_0.domain.Port.State) 
@@ -131,7 +131,7 @@ public interface PortAsyncApi {
    @SelectJson("attachment")
    @Path("/{id}/attachment")
    @ExceptionParser(ReturnNullOnNotFoundOr404.class)   
-   ListenableFuture<Attachment> showAttachment(@PathParam("id") String portId);
+   ListenableFuture<? extends Attachment> showAttachment(@PathParam("id") String portId);
 
    /**
     * @see PortApi#plugAttachment
diff --git a/labs/openstack-quantum/src/test/java/org/jclouds/openstack/quantum/v1_0/features/NetworkApiExpectTest.java b/labs/openstack-quantum/src/test/java/org/jclouds/openstack/quantum/v1_0/features/NetworkApiExpectTest.java
index da8b08717e..bf23dfb041 100644
--- a/labs/openstack-quantum/src/test/java/org/jclouds/openstack/quantum/v1_0/features/NetworkApiExpectTest.java
+++ b/labs/openstack-quantum/src/test/java/org/jclouds/openstack/quantum/v1_0/features/NetworkApiExpectTest.java
@@ -55,7 +55,7 @@ public class NetworkApiExpectTest extends BaseQuantumApiExpectTest {
             HttpResponse.builder().statusCode(200).payload(payloadFromResourceWithContentType("/list_network_refs.json", APPLICATION_JSON)).build())
             .getNetworkApiForRegion("region-a.geo-1");
       
-      Set<Reference> nets = api.listReferences();
+      Set<? extends Reference> nets = api.listReferences();
       assertEquals(nets, listOfNetworkRefs());
    }
 
@@ -76,7 +76,7 @@ public class NetworkApiExpectTest extends BaseQuantumApiExpectTest {
             HttpResponse.builder().statusCode(200).payload(payloadFromResourceWithContentType("/list_networks.json", APPLICATION_JSON)).build())
             .getNetworkApiForRegion("region-a.geo-1");
 
-      Set<Network> nets = api.list();
+      Set<? extends Network> nets = api.list();
       assertEquals(nets, listOfNetworks());
    }
 
diff --git a/labs/openstack-quantum/src/test/java/org/jclouds/openstack/quantum/v1_0/features/NetworkApiLiveTest.java b/labs/openstack-quantum/src/test/java/org/jclouds/openstack/quantum/v1_0/features/NetworkApiLiveTest.java
index a0060be346..5add5bf041 100644
--- a/labs/openstack-quantum/src/test/java/org/jclouds/openstack/quantum/v1_0/features/NetworkApiLiveTest.java
+++ b/labs/openstack-quantum/src/test/java/org/jclouds/openstack/quantum/v1_0/features/NetworkApiLiveTest.java
@@ -42,8 +42,8 @@ public class NetworkApiLiveTest extends BaseQuantumApiLiveTest {
 
    public void testListNetworks() {
       for (String regionId : quantumContext.getApi().getConfiguredRegions()) {
-         Set<Reference> ids = quantumContext.getApi().getNetworkApiForRegion(regionId).listReferences();
-         Set<Network> networks = quantumContext.getApi().getNetworkApiForRegion(regionId).list();
+         Set<? extends Reference> ids = quantumContext.getApi().getNetworkApiForRegion(regionId).listReferences();
+         Set<? extends Network> networks = quantumContext.getApi().getNetworkApiForRegion(regionId).list();
          assertNotNull(ids);
          assertEquals(ids.size(), networks.size());
          for (Network network : networks) {
diff --git a/labs/openstack-quantum/src/test/java/org/jclouds/openstack/quantum/v1_0/features/PortApiExpectTest.java b/labs/openstack-quantum/src/test/java/org/jclouds/openstack/quantum/v1_0/features/PortApiExpectTest.java
index 640b6ed431..02a61a1c3d 100644
--- a/labs/openstack-quantum/src/test/java/org/jclouds/openstack/quantum/v1_0/features/PortApiExpectTest.java
+++ b/labs/openstack-quantum/src/test/java/org/jclouds/openstack/quantum/v1_0/features/PortApiExpectTest.java
@@ -56,7 +56,7 @@ public class PortApiExpectTest extends BaseQuantumApiExpectTest {
             HttpResponse.builder().statusCode(200).payload(payloadFromStringWithContentType("{\"ports\": [{\"id\": \"a6058a59-fa8c-46cc-bac8-08904e6ff0a5\"}]}", APPLICATION_JSON)).build())
             .getPortApiForRegionAndNetwork("region-a.geo-1", "1a104cf5-cb18-4d35-9407-2fd2646d9d0b");
 
-      Set<Reference> nets = api.listReferences();
+      Set<? extends Reference> nets = api.listReferences();
       assertEquals(nets, ImmutableSet.of(Reference.builder().id("a6058a59-fa8c-46cc-bac8-08904e6ff0a5").build()));
    }
 
@@ -77,7 +77,7 @@ public class PortApiExpectTest extends BaseQuantumApiExpectTest {
             HttpResponse.builder().statusCode(200).payload(payloadFromStringWithContentType("{\"ports\": [{\"state\": \"DOWN\", \"id\": \"814ae4bb-33d9-425f-8ee2-13a5c90b1465\"}]}", APPLICATION_JSON)).build())
             .getPortApiForRegionAndNetwork("region-a.geo-1", "1a104cf5-cb18-4d35-9407-2fd2646d9d0b");
 
-      Set<Port> nets = api.list();
+      Set<? extends Port> nets = api.list();
       assertEquals(nets, ImmutableSet.of(Port.builder().state(Port.State.DOWN).id("814ae4bb-33d9-425f-8ee2-13a5c90b1465").build()));
    }
 
diff --git a/labs/openstack-quantum/src/test/java/org/jclouds/openstack/quantum/v1_0/features/PortApiLiveTest.java b/labs/openstack-quantum/src/test/java/org/jclouds/openstack/quantum/v1_0/features/PortApiLiveTest.java
index 68c92a6d83..b179061fe0 100644
--- a/labs/openstack-quantum/src/test/java/org/jclouds/openstack/quantum/v1_0/features/PortApiLiveTest.java
+++ b/labs/openstack-quantum/src/test/java/org/jclouds/openstack/quantum/v1_0/features/PortApiLiveTest.java
@@ -46,11 +46,11 @@ public class PortApiLiveTest extends BaseQuantumApiLiveTest {
    public void testListPorts() {
       for (String regionId : quantumContext.getApi().getConfiguredRegions()) {
          NetworkApi netApi = quantumContext.getApi().getNetworkApiForRegion(regionId);
-         Set<Reference> nets = netApi.listReferences();
+         Set<? extends Reference> nets = netApi.listReferences();
          for(Reference net : nets) {
             PortApi portApi = quantumContext.getApi().getPortApiForRegionAndNetwork(regionId, net.getId());
-            Set<Reference> portRefs = portApi.listReferences();
-            Set<Port> ports = portApi.list();
+            Set<? extends Reference> portRefs = portApi.listReferences();
+            Set<? extends Port> ports = portApi.list();
             
             assertEquals(portRefs.size(), ports.size());
             for (Port port : ports) {
diff --git a/labs/openstack-swift/src/main/java/org/jclouds/openstack/swift/v1/features/AccountApi.java b/labs/openstack-swift/src/main/java/org/jclouds/openstack/swift/v1/features/AccountApi.java
index 8bdbcecec4..1cf2e2b664 100644
--- a/labs/openstack-swift/src/main/java/org/jclouds/openstack/swift/v1/features/AccountApi.java
+++ b/labs/openstack-swift/src/main/java/org/jclouds/openstack/swift/v1/features/AccountApi.java
@@ -47,7 +47,7 @@ public interface AccountApi {
    /**
     * @see #listContainers(ListContainersOptions)
     */
-   Set<ContainerMetadata> listContainers();
+   Set<? extends ContainerMetadata> listContainers();
 
    /**
     * retrieve a list of existing storage containers ordered by name. The sort order for the name is
@@ -57,6 +57,6 @@ public interface AccountApi {
     * @param options
     * @return a list of existing storage containers ordered by name.
     */
-   Set<ContainerMetadata> listContainers(ListContainersOptions options);
+   Set<? extends ContainerMetadata> listContainers(ListContainersOptions options);
 
 }
diff --git a/labs/openstack-swift/src/main/java/org/jclouds/openstack/swift/v1/features/AccountAsyncApi.java b/labs/openstack-swift/src/main/java/org/jclouds/openstack/swift/v1/features/AccountAsyncApi.java
index 542fff1357..de64deef66 100644
--- a/labs/openstack-swift/src/main/java/org/jclouds/openstack/swift/v1/features/AccountAsyncApi.java
+++ b/labs/openstack-swift/src/main/java/org/jclouds/openstack/swift/v1/features/AccountAsyncApi.java
@@ -59,7 +59,7 @@ public interface AccountAsyncApi {
    @HEAD
    @ResponseParser(ParseAccountMetadataResponseFromHeaders.class)
    @Path("/")
-   ListenableFuture<AccountMetadata> getAccountMetadata();
+   ListenableFuture<? extends AccountMetadata> getAccountMetadata();
 
    /**
     * @see AccountApi#listContainers()
@@ -69,7 +69,7 @@ public interface AccountAsyncApi {
    @QueryParams(keys = "format", values = "json")
    @ExceptionParser(ReturnEmptySetOnNotFoundOr404.class)
    @Path("/")
-   ListenableFuture<Set<ContainerMetadata>> listContainers();
+   ListenableFuture<? extends Set<? extends ContainerMetadata>> listContainers();
 
    /**
     * @see AccountApi#listContainers(ListContainersOptions)
@@ -79,5 +79,5 @@ public interface AccountAsyncApi {
    @QueryParams(keys = "format", values = "json")
    @ExceptionParser(ReturnEmptySetOnNotFoundOr404.class)
    @Path("/")
-   ListenableFuture<Set<ContainerMetadata>> listContainers(ListContainersOptions options);
+   ListenableFuture<? extends Set<? extends ContainerMetadata>> listContainers(ListContainersOptions options);
 }
diff --git a/labs/openstack-swift/src/test/java/org/jclouds/openstack/swift/v1/features/AccountApiLiveTest.java b/labs/openstack-swift/src/test/java/org/jclouds/openstack/swift/v1/features/AccountApiLiveTest.java
index c3633dd096..8521c0e236 100644
--- a/labs/openstack-swift/src/test/java/org/jclouds/openstack/swift/v1/features/AccountApiLiveTest.java
+++ b/labs/openstack-swift/src/test/java/org/jclouds/openstack/swift/v1/features/AccountApiLiveTest.java
@@ -49,7 +49,7 @@ public class AccountApiLiveTest extends BaseSwiftApiLiveTest {
    public void testListContainers() throws Exception {
       for (String regionId : swiftContext.getApi().getConfiguredRegions()) {
          AccountApi api = swiftContext.getApi().getAccountApiForRegion(regionId);
-         Set<ContainerMetadata> response = api.listContainers();
+         Set<? extends ContainerMetadata> response = api.listContainers();
          assertNotNull(response);
          for (ContainerMetadata container : response) {
             assertNotNull(container.getName());