diff --git a/bundles/org.eclipse.wst.xsd.ui/src-adt-xsd/org/eclipse/wst/xsd/ui/internal/editor/KeyboardDragImpl.java b/bundles/org.eclipse.wst.xsd.ui/src-adt-xsd/org/eclipse/wst/xsd/ui/internal/editor/KeyboardDragImpl.java
index a5dc0fa..c0fc8e3 100644
--- a/bundles/org.eclipse.wst.xsd.ui/src-adt-xsd/org/eclipse/wst/xsd/ui/internal/editor/KeyboardDragImpl.java
+++ b/bundles/org.eclipse.wst.xsd.ui/src-adt-xsd/org/eclipse/wst/xsd/ui/internal/editor/KeyboardDragImpl.java
@@ -36,6 +36,9 @@
     policy = (KeyBoardAccessibilityEditPolicy) rightElement.getEditPolicy(KeyBoardAccessibilityEditPolicy.KEY);
     EditPart leftElement = (policy != null) ? policy.getRelativeEditPart(rightElement, direction) : null;
 
+    // TODO: add support for extenders
+    if (!(movingElement instanceof XSDBaseFieldEditPart)) return;
+    
     XSDBaseFieldEditPart movingField = (XSDBaseFieldEditPart) movingElement;
     XSDBaseFieldEditPart leftField = (XSDBaseFieldEditPart) leftElement;
     XSDBaseFieldEditPart rightField = (XSDBaseFieldEditPart) rightElement;