fix serialize

diff --git a/lib/sqlalchemy/types.py b/lib/sqlalchemy/types.py
index 8d47a2cf5d37a2232c72d186c9b44c6f13bb1826..a03d6137dfa93d7204c0e43a4061c30f26a4d698 100644 (file)
--- a/lib/sqlalchemy/types.py
+++ b/lib/sqlalchemy/types.py
@@ -132,7 +132,7 @@ class TypeEngine(AbstractType):
 
     def __getstate__(self):
         d = self.__dict__.copy()
-        d['_impl_dict'] = weakref.WeakKeyDictionary()   # will be optimized in 0.6
+        d.pop('_impl_dict', None)
         return d
 
     def get_col_spec(self):