diff --git a/mercurial/windows.py b/mercurial/windows.py
--- a/mercurial/windows.py
+++ b/mercurial/windows.py
@@ -62,7 +62,7 @@ class winstdout(object):
             self.close()
             raise IOError(errno.EPIPE, 'Broken pipe')
 
-sys.stdout = winstdout(sys.stdout)
+sys.__stdout__ = sys.stdout = winstdout(sys.stdout)
 
 def _is_win_9x():
     '''return true if run on windows 95, 98 or me.'''