diff --git a/Lib/pickle.py b/Lib/pickle.py
index 4bc54ec..d4085cf 100644
--- a/Lib/pickle.py
+++ b/Lib/pickle.py
@@ -626,6 +626,8 @@
         return classmap[cls]
 
     for name, module in sys.modules.items():
+        if module is None: 
+            continue # skip dummy package entries
         if name != '__main__' and \
             hasattr(module, clsname) and \
             getattr(module, clsname) is cls: