diff --git a/rhodecode/model/db.py b/rhodecode/model/db.py
--- a/rhodecode/model/db.py
+++ b/rhodecode/model/db.py
@@ -425,7 +425,8 @@ class UsersGroup( Base, BaseModel ):
                     Session.flush()
                     members_list = []
                     if v:
-                        for u_id in set( list( v ) ):
+                        v = [v] if isinstance(v, basestring) else v
+                        for u_id in set(v):
                             member = UsersGroupMember( users_group_id, u_id )
                             members_list.append( member )
                     setattr( users_group, 'members', members_list )