for UserDict to be compatible with abcs, it must subclass object
diff --git a/Lib/UserDict.py b/Lib/UserDict.py
index 0d9591a..df5f7fb 100644
--- a/Lib/UserDict.py
+++ b/Lib/UserDict.py
@@ -1,6 +1,6 @@
 """A more or less complete user-defined wrapper around dictionary objects."""
 
-class UserDict:
+class UserDict(object):
     def __init__(self, dict=None, **kwargs):
         self.data = {}
         if dict is not None: