diff --git a/hgext/win32mbcs.py b/hgext/win32mbcs.py
--- a/hgext/win32mbcs.py
+++ b/hgext/win32mbcs.py
@@ -155,7 +155,8 @@ funcs = '''os.path.join os.path.split os
 # These functions are required to be called with local encoded string
 # because they expects argument is local encoded string and cause
 # problem with unicode string.
-rfuncs = '''mercurial.encoding.upper mercurial.encoding.lower'''
+rfuncs = '''mercurial.encoding.upper mercurial.encoding.lower
+ mercurial.pycompat.bytestr'''
 
 # List of Windows specific functions to be wrapped.
 winfuncs = '''os.path.splitunc'''