diff --git a/Lib/copy_reg.py b/Lib/copy_reg.py
index 92cbd53..8a3550a 100644
--- a/Lib/copy_reg.py
+++ b/Lib/copy_reg.py
@@ -53,6 +53,8 @@
     if base is object:
         state = None
     else:
+        if base is self.__class__:
+            raise TypeError, "can't pickle %s objects" % base.__name__
         state = base(self)
     args = (self.__class__, base, state)
     try: