Index: generic.py
===================================================================
--- generic.py  (revision 5818)
+++ generic.py  (working copy)
@@ -118,7 +118,7 @@
         return self.object_id_field_name

     def m2m_reverse_name(self):
-        return self.object_id_field_name
+       return self.model._meta.pk.attname

     def contribute_to_class(self, cls, name):
         super(GenericRelation, self).contribute_to_class(cls, name)