diff --git a/src/core/object.cc b/src/core/object.cc
index 4a9e66218..1c6d58772 100644
--- a/src/core/object.cc
+++ b/src/core/object.cc
@@ -192,6 +192,7 @@ Object::~Object ()
 Ptr<Object>
 Object::DoQueryInterface (InterfaceId iid) const
 {
+  NS_ASSERT (Check ());
   const Object *currentObject = this;
   do {
     NS_ASSERT (currentObject != 0);