diff -r ec7818110fd2 -r db306bbda381 app/soc/models/grading_survey_group.py
--- a/app/soc/models/grading_survey_group.py	Tue Jul 07 20:17:23 2009 -0500
+++ b/app/soc/models/grading_survey_group.py	Sat Jul 11 13:56:55 2009 +0200
@@ -56,12 +56,12 @@
 
   #: GradingProjectSurvey which belongs to this group.
   grading_survey = db.ReferenceProperty(
-      GradingProjectSurvey, required=True,
+      reference_class=GradingProjectSurvey, required=True,
       collection_name='grading_survey_groups')
 
   #: non-required ProjectSurvey that belongs to this group.
   student_survey = db.ReferenceProperty(
-      ProjectSurvey, required=False,
+      reference_class=ProjectSurvey, required=False,
       collection_name='project_survey_groups')
 
   #: DateTime when the last GradingRecord update was started for this group.