for modelclass, idlist in idlist_per_model.items():
             qs = modelclass.base_objects.filter(id__in=idlist)
             qs.dup_select_related(self)    # copy select related configuration to new qs

             for o in qs:
+                if type(o.pk) != type(o.id):
+                    o.pk=o.id
+
                 if self.query.aggregates:
                     for anno_field_name in self.query.aggregates.keys():
                         attr = getattr(base_result_objects_by_id[o.pk], anno_field_name)
                         setattr(o, anno_field_name, attr)