diff --git a/maven-core/src/main/java/org/apache/maven/listeners/BuildExtensionListener.java b/maven-core/src/main/java/org/apache/maven/listeners/BuildExtensionListener.java
index 4865944da7..a47b4eeac5 100644
--- a/maven-core/src/main/java/org/apache/maven/listeners/BuildExtensionListener.java
+++ b/maven-core/src/main/java/org/apache/maven/listeners/BuildExtensionListener.java
@@ -45,7 +45,7 @@ public class BuildExtensionListener
     
     private List<BuildExtension> buildExtensions = new ArrayList<BuildExtension>();
     
-    public void fire( List<ModelContainer> modelContainers )
+    public void fire( List<? extends ModelContainer> modelContainers )
     {        
         if ( !inBuild )
         {
diff --git a/maven-project-builder/src/main/java/org/apache/maven/project/builder/PomTransformer.java b/maven-project-builder/src/main/java/org/apache/maven/project/builder/PomTransformer.java
index ce57834832..4ba0fd7330 100644
--- a/maven-project-builder/src/main/java/org/apache/maven/project/builder/PomTransformer.java
+++ b/maven-project-builder/src/main/java/org/apache/maven/project/builder/PomTransformer.java
@@ -103,7 +103,7 @@ public class PomTransformer
     /**
      * @see ModelTransformer#transformToDomainModel(java.util.List, java.util.List)
      */
-    public final DomainModel transformToDomainModel( List<ModelProperty> properties,  List<ModelEventListener> eventListeners )
+    public final DomainModel transformToDomainModel( List<ModelProperty> properties,  List<? extends ModelEventListener> eventListeners )
         throws IOException
     {
         if ( properties == null )
@@ -298,7 +298,7 @@ public class PomTransformer
     /**
      * @see ModelTransformer#transformToModelProperties(java.util.List)
      */
-    public final List<ModelProperty> transformToModelProperties(List<DomainModel> domainModels
+    public final List<ModelProperty> transformToModelProperties(List<? extends DomainModel> domainModels
     )
         throws IOException
     {