diff --git a/lib/sqlalchemy/types.py b/lib/sqlalchemy/types.py
index a03bf41bf4..3b08cf6f38 100644
--- a/lib/sqlalchemy/types.py
+++ b/lib/sqlalchemy/types.py
@@ -17,7 +17,7 @@ __all__ = [ 'TypeEngine', 'TypeDecorator', 'AbstractType',
             'BOOLEAN', 'SMALLINT', 'DATE', 'TIME',
             'String', 'Integer', 'SmallInteger','Smallinteger',
             'Numeric', 'Float', 'DateTime', 'Date', 'Time', 'Binary',
-            'Boolean', 'Unicode', 'UnicodeText', 'PickleType', 'Interval',
+            'Boolean', 'Unicode', 'MutableType', 'Concatenable', 'UnicodeText', 'PickleType', 'Interval',
             'type_map'
             ]