Index: Objects/typeobject.c
===================================================================
--- Objects/typeobject.c	(revision 59568)
+++ Objects/typeobject.c	(working copy)
@@ -469,8 +469,10 @@
 	else
 		(void) PyObject_INIT_VAR((PyVarObject *)obj, type, nitems);
 
-	if (PyType_IS_GC(type))
+	if (PyType_IS_GC(type)) {
+		assert(type->tp_traverse);
 		_PyObject_GC_TRACK(obj);
+	}
 	return obj;
 }