--- a/src/core/object.cc	Fri Sep 28 19:13:19 2007 +0100
+++ b/src/core/object.cc	Mon Oct 01 11:42:41 2007 +0100
@@ -192,6 +192,7 @@
 Ptr<Object>
 Object::DoQueryInterface (InterfaceId iid) const
 {
+  NS_ASSERT (Check ());
   const Object *currentObject = this;
   do {
     NS_ASSERT (currentObject != 0);