adjustments...

2 files changed, 6 insertions, 3 deletions

diff --git a/lib/sqlalchemy/mapping/mapper.py b/lib/sqlalchemy/mapping/mapper.py
index 0f2b4e19f..a9f7df63c 100644
--- a/lib/sqlalchemy/mapping/mapper.py
+++ b/lib/sqlalchemy/mapping/mapper.py
@@ -58,9 +58,10 @@ class Mapper(object):
         
         for ext_class in global_extensions:
             ext = ext_class().chain(ext)
-        
-        for ext_obj in util.to_list(extension):
-            ext = ext_obj.chain(ext)
+
+        if extension is not None:
+            for ext_obj in util.to_list(extension):
+                ext = ext_obj.chain(ext)
             
         self.extension = ext
 
diff --git a/lib/sqlalchemy/mods/selectresults.py b/lib/sqlalchemy/mods/selectresults.py
index 1f6b77a25..b4f16c41c 100644
--- a/lib/sqlalchemy/mods/selectresults.py
+++ b/lib/sqlalchemy/mods/selectresults.py
@@ -13,6 +13,8 @@ class SelectResultsExt(mapping.MapperExtension):
             return mapping.EXT_PASS
         else:
             return SelectResults(mapper, arg, ops=kwargs)
+
+MapperExtension = SelectResultsExt
         
 class SelectResults(object):
     def __init__(self, mapper, clause=None, ops={}):