diff --git a/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/DeviceDetails.java b/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/DeviceDetails.java
index f10a5ec873..fca976cd97 100644
--- a/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/DeviceDetails.java
+++ b/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/DeviceDetails.java
@@ -42,6 +42,7 @@ public class DeviceDetails {
    private final DeviceType deviceType;
 
    public DeviceDetails(int port, int deviceSlot, DeviceType deviceType) {
+      checkNotNull(deviceType, "deviceType");
       this.port = port;
       this.deviceSlot = deviceSlot;
       this.deviceType = deviceType;
diff --git a/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/IsoImage.java b/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/IsoImage.java
index 2bafab7015..529535ce38 100644
--- a/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/IsoImage.java
+++ b/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/IsoImage.java
@@ -21,6 +21,8 @@ package org.jclouds.virtualbox.domain;
 
 import com.google.common.base.Objects;
 
+import static com.google.common.base.Preconditions.checkNotNull;
+
 /**
  * Represents an optical medium (DVD) in a VirtualBox VM.
  * <p/>
@@ -32,6 +34,8 @@ public class IsoImage {
    private String sourcePath;
 
    public IsoImage(DeviceDetails deviceDetails, String sourcePath) {
+      checkNotNull(deviceDetails, "deviceDetails");
+      checkNotNull(sourcePath, "sourcePath");
       this.deviceDetails = deviceDetails;
       this.sourcePath = sourcePath;
    }
diff --git a/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/NatAdapter.java b/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/NatAdapter.java
index d41c7daac8..18df5527b6 100644
--- a/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/NatAdapter.java
+++ b/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/NatAdapter.java
@@ -26,6 +26,8 @@ import org.virtualbox_4_1.NATProtocol;
 import java.util.Collections;
 import java.util.Set;
 
+import static com.google.common.base.Preconditions.checkNotNull;
+
 /**
  * Represents a NAT network adapter in VirtualBox.
  * <p/>
@@ -36,6 +38,7 @@ public class NatAdapter {
    private final Set<RedirectRule> redirectRules = Sets.newLinkedHashSet();
 
    public NatAdapter(Set<RedirectRule> redirectRules) {
+      checkNotNull(redirectRules);
       this.redirectRules.addAll(redirectRules);
    }
 
diff --git a/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/RedirectRule.java b/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/RedirectRule.java
index a151114647..e52b3b9a98 100644
--- a/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/RedirectRule.java
+++ b/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/RedirectRule.java
@@ -22,6 +22,8 @@ package org.jclouds.virtualbox.domain;
 import com.google.common.base.Objects;
 import org.virtualbox_4_1.NATProtocol;
 
+import static com.google.common.base.Preconditions.checkNotNull;
+
 /**
  * @author Mattias Holmqvist
  */
@@ -34,6 +36,9 @@ public class RedirectRule {
    private final int guestPort;
 
    public RedirectRule(NATProtocol protocol, String host, int hostPort, String guest, int guestPort) {
+      checkNotNull(protocol);
+      checkNotNull(host);
+      checkNotNull(guest);
       this.protocol = protocol;
       this.host = host;
       this.hostPort = hostPort;
diff --git a/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/StorageController.java b/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/StorageController.java
index aa15c85cae..7bdcd6a7f1 100644
--- a/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/StorageController.java
+++ b/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/StorageController.java
@@ -19,6 +19,7 @@
 
 package org.jclouds.virtualbox.domain;
 
+import com.google.common.base.Objects;
 import org.virtualbox_4_1.DeviceType;
 import org.virtualbox_4_1.StorageBus;
 
@@ -30,7 +31,7 @@ import static org.jclouds.virtualbox.domain.HardDisk.DEFAULT_DISK_FORMAT;
 
 /**
  * Represents a storage controller in a VirtualBox VM.
- *
+ * <p/>
  * name is the unique name of the controller.
  * bus is the type of connection bus for the controller
  * hardDisks contains the hard disks that are attached (or should be attached) to this controller
@@ -45,6 +46,10 @@ public class StorageController {
    private Set<IsoImage> isoImages;
 
    public StorageController(String name, StorageBus bus, Set<HardDisk> hardDisks, Set<IsoImage> isoImages) {
+      checkNotNull(name, "name");
+      checkNotNull(bus, "bus");
+      checkNotNull(hardDisks, "hardDisks");
+      checkNotNull(isoImages, "isoImages");
       this.name = name;
       this.bus = bus;
       this.hardDisks = hardDisks;
@@ -70,25 +75,19 @@ public class StorageController {
    @Override
    public boolean equals(Object o) {
       if (this == o) return true;
-      if (o == null || getClass() != o.getClass()) return false;
-
-      StorageController that = (StorageController) o;
-
-      if (bus != that.bus) return false;
-      if (isoImages != null ? !isoImages.equals(that.isoImages) : that.isoImages != null) return false;
-      if (hardDisks != null ? !hardDisks.equals(that.hardDisks) : that.hardDisks != null) return false;
-      if (name != null ? !name.equals(that.name) : that.name != null) return false;
-
-      return true;
+      if (o instanceof StorageController) {
+         StorageController other = (StorageController) o;
+         return Objects.equal(name, other.name) &&
+                 Objects.equal(bus, other.bus) &&
+                 Objects.equal(hardDisks, other.hardDisks) &&
+                 Objects.equal(isoImages, other.isoImages);
+      }
+      return false;
    }
 
    @Override
    public int hashCode() {
-      int result = name != null ? name.hashCode() : 0;
-      result = 31 * result + (bus != null ? bus.hashCode() : 0);
-      result = 31 * result + (hardDisks != null ? hardDisks.hashCode() : 0);
-      result = 31 * result + (isoImages != null ? isoImages.hashCode() : 0);
-      return result;
+      return Objects.hashCode(name, bus, hardDisks, isoImages);
    }
 
    @Override
diff --git a/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/VmSpec.java b/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/VmSpec.java
index 7ae269598d..cafccf50a2 100644
--- a/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/VmSpec.java
+++ b/sandbox-apis/virtualbox/src/main/java/org/jclouds/virtualbox/domain/VmSpec.java
@@ -25,6 +25,7 @@ import java.util.*;
 
 import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkNotNull;
+import static com.google.common.base.Preconditions.checkState;
 
 /**
  * A description of a Virtual Machine in VirtualBox.
@@ -40,6 +41,11 @@ public class VmSpec {
    private final Set<StorageController> controllers;
 
    public VmSpec(String vmId, String vmName, String osTypeId, long memory, boolean forceOverwrite, Set<StorageController> controllers, Map<Long, NatAdapter> natNetworkAdapters) {
+      checkNotNull(vmId, "vmId");
+      checkNotNull(vmName, "vmName");
+      checkArgument(memory > 0, "memory must be > 0");
+      checkNotNull(controllers, "controllers");
+      checkNotNull(natNetworkAdapters, "natNetworkAdapters");
       this.vmId = vmId;
       this.vmName = vmName;
       this.osTypeId = osTypeId;