added an assertion to prevent against the use in [ticket:1048]

3 files changed, 9 insertions, 1 deletions

diff --git a/lib/sqlalchemy/orm/mapper.py b/lib/sqlalchemy/orm/mapper.py
index 72edc4e4b..c0a73e2b2 100644
--- a/lib/sqlalchemy/orm/mapper.py
+++ b/lib/sqlalchemy/orm/mapper.py
@@ -253,6 +253,9 @@ class Mapper(object):
             mappers = list(self.polymorphic_iterator())
         elif spec:
             mappers = [_class_to_mapper(m) for m in util.to_list(spec)]
+            for m in mappers:
+                if not m.isa(self):
+                    raise sa_exc.InvalidRequestError("%r does not inherit from %r"  % (m, self))
         else:
             mappers = []
 
diff --git a/lib/sqlalchemy/orm/query.py b/lib/sqlalchemy/orm/query.py
index 47d00964d..5df13d8d9 100644
--- a/lib/sqlalchemy/orm/query.py
+++ b/lib/sqlalchemy/orm/query.py
@@ -1381,7 +1381,7 @@ class _MapperEntity(_QueryEntity):
         if cls_or_mappers is None:
             query._reset_polymorphic_adapter(self.mapper)
             return
-
+        
         mappers, from_obj = self.mapper._with_polymorphic_args(cls_or_mappers, selectable)
         self._with_polymorphic = mappers
 
diff --git a/test/orm/inheritance/query.py b/test/orm/inheritance/query.py
index 62d315e71..1cf09582e 100644
--- a/test/orm/inheritance/query.py
+++ b/test/orm/inheritance/query.py
@@ -303,6 +303,11 @@ def make_test(select_type):
             
             sess = create_session()
             
+            
+            self.assertRaises(sa_exc.InvalidRequestError, sess.query(Person).with_polymorphic, Paperwork)
+            self.assertRaises(sa_exc.InvalidRequestError, sess.query(Engineer).with_polymorphic, Boss)
+            self.assertRaises(sa_exc.InvalidRequestError, sess.query(Engineer).with_polymorphic, Person)
+            
             # compare to entities without related collections to prevent additional lazy SQL from firing on 
             # loaded entities
             emps_without_relations = [