--- a/mercurial/util_win32.py
+++ b/mercurial/util_win32.py
@@ -297,3 +297,5 @@ class posixfile_nt(object):
             win32file.SetEndOfFile(self.handle)
         except pywintypes.error, err:
             raise WinIOError(err)
+
+getuser_fallback = win32api.GetUserName