diff -r cda93720c06d Lib/pydoc.py
--- a/Lib/pydoc.py	Sat Jul 23 18:15:43 2011 +0200
+++ b/Lib/pydoc.py	Sat Jul 23 18:53:49 2011 +0200
@@ -218,8 +218,8 @@
 def synopsis(filename, cache={}):
     """Get the one-line summary out of a module file."""
     mtime = os.stat(filename).st_mtime
-    lastupdate, result = cache.get(filename, (0, None))
-    if lastupdate < mtime:
+    lastupdate, result = cache.get(filename, (None, None))
+    if lastupdate is None or lastupdate < mtime:
         info = inspect.getmoduleinfo(filename)
         try:
             file = tokenize.open(filename)