Index: Lib/trace.py
===================================================================
--- Lib/trace.py	(revision 88110)
+++ Lib/trace.py	(working copy)
@@ -135,7 +135,7 @@
         self._mods = modules or []
         self._dirs = dirs or []
 
-        self._dirs = map(os.path.normpath, self._dirs)
+        self._dirs = [os.path.normcase(os.path.normpath(d)) for d in self._dirs]
         self._ignore = { '<string>': 1 }
 
     def names(self, filename, modulename):
@@ -166,6 +166,8 @@
             self._ignore[modulename] = 1
             return 1
 
+        filename = os.path.normcase(filename)
+
         # Ignore a file when it contains one of the ignorable paths
         for d in self._dirs:
             # The '+ os.sep' is to ensure that d is a parent directory,