--- a/vregistry.py	Wed Feb 18 00:45:29 2009 +0100
+++ b/vregistry.py	Wed Feb 18 00:48:24 2009 +0100
@@ -235,6 +235,7 @@
         assert not '__abstract__' in obj.__dict__
         registryname = registryname or obj.__registry__
         oid = oid or obj.id
+        assert oid
         registry = self._registries.setdefault(registryname, {})
         if clear:
             vobjects = registry[oid] =  []