diff -r 919259054621 Lib/inspect.py
--- a/Lib/inspect.py	Sun Nov 27 00:19:53 2011 +0100
+++ b/Lib/inspect.py	Sat Nov 26 18:49:16 2011 -0800
@@ -482,7 +482,7 @@
         return sys.modules.get(modulesbyfile[file])
     # Update the filename to module name cache and check yet again
     # Copy sys.modules in order to cope with changes while iterating
-    for modname, module in sys.modules.items():
+    for modname, module in list(sys.modules.items()):
         if ismodule(module) and hasattr(module, '__file__'):
             f = module.__file__
             if f == _filesbymodname.get(modname, None):