diff --git a/pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/impl/javacc/AbstractJjtreeNode.java b/pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/impl/javacc/AbstractJjtreeNode.java
index 4f8b246e85..f01249cece 100644
--- a/pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/impl/javacc/AbstractJjtreeNode.java
+++ b/pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/impl/javacc/AbstractJjtreeNode.java
@@ -43,7 +43,7 @@ public abstract class AbstractJjtreeNode<N extends Node> extends AbstractNode {
 
     @Override
     @SuppressWarnings("unchecked")
-    public Iterable<N> children() {
+    public Iterable<? extends N> children() {
         return (Iterable<N>) super.children();
     }
 }
diff --git a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/ast/JavaNode.java b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/ast/JavaNode.java
index 1524f6d53d..b8310ea936 100644
--- a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/ast/JavaNode.java
+++ b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/ast/JavaNode.java
@@ -51,7 +51,7 @@ public interface JavaNode extends ScopedNode {
 
 
     @Override
-    Iterable<JavaNode> children();
+    Iterable<? extends JavaNode> children();
 
 
     @InternalApi
diff --git a/pmd-jsp/src/main/java/net/sourceforge/pmd/lang/jsp/ast/JspNode.java b/pmd-jsp/src/main/java/net/sourceforge/pmd/lang/jsp/ast/JspNode.java
index e0a2fbe195..bc4d3db106 100644
--- a/pmd-jsp/src/main/java/net/sourceforge/pmd/lang/jsp/ast/JspNode.java
+++ b/pmd-jsp/src/main/java/net/sourceforge/pmd/lang/jsp/ast/JspNode.java
@@ -32,5 +32,5 @@ public interface JspNode extends Node {
 
 
     @Override
-    Iterable<JspNode> children();
+    Iterable<? extends JspNode> children();
 }
diff --git a/pmd-modelica/src/main/java/net/sourceforge/pmd/lang/modelica/ast/ModelicaNode.java b/pmd-modelica/src/main/java/net/sourceforge/pmd/lang/modelica/ast/ModelicaNode.java
index b212a2a55d..bbc13218ae 100644
--- a/pmd-modelica/src/main/java/net/sourceforge/pmd/lang/modelica/ast/ModelicaNode.java
+++ b/pmd-modelica/src/main/java/net/sourceforge/pmd/lang/modelica/ast/ModelicaNode.java
@@ -35,5 +35,5 @@ public interface ModelicaNode extends Node {
 
 
     @Override
-    Iterable<ModelicaNode> children();
+    Iterable<? extends ModelicaNode> children();
 }
diff --git a/pmd-plsql/src/main/java/net/sourceforge/pmd/lang/plsql/ast/PLSQLNode.java b/pmd-plsql/src/main/java/net/sourceforge/pmd/lang/plsql/ast/PLSQLNode.java
index 6538263fba..bfd4e4ae89 100644
--- a/pmd-plsql/src/main/java/net/sourceforge/pmd/lang/plsql/ast/PLSQLNode.java
+++ b/pmd-plsql/src/main/java/net/sourceforge/pmd/lang/plsql/ast/PLSQLNode.java
@@ -36,5 +36,5 @@ public interface PLSQLNode extends Node, ScopedNode {
 
 
     @Override
-    Iterable<PLSQLNode> children();
+    Iterable<? extends PLSQLNode> children();
 }
diff --git a/pmd-scala/src/main/java/net/sourceforge/pmd/lang/scala/ast/AbstractScalaNode.java b/pmd-scala/src/main/java/net/sourceforge/pmd/lang/scala/ast/AbstractScalaNode.java
index 587d962da4..d895bd8389 100644
--- a/pmd-scala/src/main/java/net/sourceforge/pmd/lang/scala/ast/AbstractScalaNode.java
+++ b/pmd-scala/src/main/java/net/sourceforge/pmd/lang/scala/ast/AbstractScalaNode.java
@@ -34,7 +34,7 @@ abstract class AbstractScalaNode<T extends Tree> extends AbstractNode implements
 
     @Override
     @SuppressWarnings("unchecked")
-    public Iterable<ScalaNode<?>> children() {
+    public Iterable<? extends ScalaNode<?>> children() {
         return (Iterable<ScalaNode<?>>) super.children();
     }
 
diff --git a/pmd-scala/src/main/java/net/sourceforge/pmd/lang/scala/ast/ScalaNode.java b/pmd-scala/src/main/java/net/sourceforge/pmd/lang/scala/ast/ScalaNode.java
index 408bd10dda..6300050812 100644
--- a/pmd-scala/src/main/java/net/sourceforge/pmd/lang/scala/ast/ScalaNode.java
+++ b/pmd-scala/src/main/java/net/sourceforge/pmd/lang/scala/ast/ScalaNode.java
@@ -62,5 +62,5 @@ public interface ScalaNode<T extends Tree> extends Node {
 
 
     @Override
-    Iterable<ScalaNode<?>> children();
+    Iterable<? extends ScalaNode<?>> children();
 }
diff --git a/pmd-visualforce/src/main/java/net/sourceforge/pmd/lang/vf/ast/VfNode.java b/pmd-visualforce/src/main/java/net/sourceforge/pmd/lang/vf/ast/VfNode.java
index e75e15b551..50367e43b4 100644
--- a/pmd-visualforce/src/main/java/net/sourceforge/pmd/lang/vf/ast/VfNode.java
+++ b/pmd-visualforce/src/main/java/net/sourceforge/pmd/lang/vf/ast/VfNode.java
@@ -34,5 +34,5 @@ public interface VfNode extends Node {
 
 
     @Override
-    Iterable<VfNode> children();
+    Iterable<? extends VfNode> children();
 }
diff --git a/pmd-vm/src/main/java/net/sourceforge/pmd/lang/vm/ast/VmNode.java b/pmd-vm/src/main/java/net/sourceforge/pmd/lang/vm/ast/VmNode.java
index a5006e93bd..f549cdb3a3 100644
--- a/pmd-vm/src/main/java/net/sourceforge/pmd/lang/vm/ast/VmNode.java
+++ b/pmd-vm/src/main/java/net/sourceforge/pmd/lang/vm/ast/VmNode.java
@@ -32,6 +32,6 @@ public interface VmNode extends Node {
 
 
     @Override
-    Iterable<VmNode> children();
+    Iterable<? extends VmNode> children();
 
 }