diff --git a/pmd-core/src/main/java/net/sourceforge/pmd/util/designer/Designer.java b/pmd-core/src/main/java/net/sourceforge/pmd/util/designer/Designer.java
index b6732a2f93..10c93de09b 100644
--- a/pmd-core/src/main/java/net/sourceforge/pmd/util/designer/Designer.java
+++ b/pmd-core/src/main/java/net/sourceforge/pmd/util/designer/Designer.java
@@ -426,7 +426,7 @@ public class Designer implements ClipboardOwner {
 			// Traverse children
 			TreeNode node = (TreeNode) parent.getLastPathComponent();
 			if (node.getChildCount() >= 0) {
-				for (Enumeration<TreeNode> e = node.children(); e.hasMoreElements();) {
+				for (Enumeration<? extends TreeNode> e = node.children(); e.hasMoreElements();) {
 					TreeNode n = e.nextElement();
 					TreePath path = parent.pathByAddingChild(n);
 					expandAll(path, expand);