diff --git a/datajoint/autopopulate.py b/datajoint/autopopulate.py
index 1556df13b..4ac2b767f 100644
--- a/datajoint/autopopulate.py
+++ b/datajoint/autopopulate.py
@@ -69,6 +69,9 @@ def _jobs_to_do(self, restrictions):
         """
         :return: the relation containing the keys to be computed (derived from self.key_source)
         """
+        if self.restriction:
+            raise DataJointError('Cannot call populate on a restricted table. '
+                                 'Instead, pass conditions to populate() as arguments.')
         todo = self.key_source
         if not isinstance(todo, RelationalOperand):
             raise DataJointError('Invalid key_source value')
diff --git a/datajoint/user_relations.py b/datajoint/user_relations.py
index df9228d55..b24d85ecb 100644
--- a/datajoint/user_relations.py
+++ b/datajoint/user_relations.py
@@ -12,7 +12,7 @@
 
 # attributes that trigger instantiation of user classes
 supported_class_attrs = set((
-    'key_source', 'describe', 'populate', 'progress',
+    'key_source', 'describe', 'populate', 'progress', 'primary_key',
     'proj', 'aggr', 'heading', 'fetch', 'fetch1',
     'insert', 'insert1', 'drop', 'drop_quick',
     'delete', 'delete_quick'))