--- a/graal/com.oracle.truffle.object/src/com/oracle/truffle/object/ShapeImpl.java	Wed Jun 10 20:05:52 2015 +0200
+++ b/graal/com.oracle.truffle.object/src/com/oracle/truffle/object/ShapeImpl.java	Wed Jun 10 20:06:13 2015 +0200
@@ -39,6 +39,7 @@
 import com.oracle.truffle.object.Locations.DualLocation;
 import com.oracle.truffle.object.Locations.ValueLocation;
 import com.oracle.truffle.object.Transition.AddPropertyTransition;
+import com.oracle.truffle.object.Transition.DirectReplacePropertyTransition;
 import com.oracle.truffle.object.Transition.ObjectTypeTransition;
 import com.oracle.truffle.object.Transition.PropertyTransition;
 import com.oracle.truffle.object.Transition.RemovePropertyTransition;
@@ -311,7 +312,7 @@
         return propertyMap;
     }
 
-    private ShapeImpl queryTransition(Transition transition) {
+    protected final ShapeImpl queryTransition(Transition transition) {
         ShapeImpl cachedShape = this.getTransitionMapForRead().get(transition);
         if (cachedShape != null) { // Shape already exists?
             shapeCacheHitCount.inc();
@@ -674,6 +675,8 @@
             return changeType(((ObjectTypeTransition) transition).getObjectType());
         } else if (transition instanceof ReservePrimitiveArrayTransition) {
             return reservePrimitiveExtensionArray();
+        } else if (transition instanceof DirectReplacePropertyTransition) {
+            return replaceProperty(((DirectReplacePropertyTransition) transition).getPropertyBefore(), ((DirectReplacePropertyTransition) transition).getPropertyAfter());
         } else {
             throw new UnsupportedOperationException();
         }
@@ -688,8 +691,10 @@
      * Duplicate shape exchanging existing property with new property.
      */
     @Override
-    public final ShapeImpl replaceProperty(Property oldProperty, Property newProperty) {
-        Transition replacePropertyTransition = new Transition.ReplacePropertyTransition(oldProperty, newProperty);
+    public ShapeImpl replaceProperty(Property oldProperty, Property newProperty) {
+        assert oldProperty.getKey().equals(newProperty.getKey());
+
+        Transition replacePropertyTransition = new Transition.IndirectReplacePropertyTransition(oldProperty, newProperty);
         ShapeImpl cachedShape = queryTransition(replacePropertyTransition);
         if (cachedShape != null) {
             return cachedShape;