diff --git a/mercurial/ui.py b/mercurial/ui.py
--- a/mercurial/ui.py
+++ b/mercurial/ui.py
@@ -392,7 +392,7 @@
     def readconfig(self, filename, root=None, trust=False,
                    sections=None, remap=None):
         try:
-            fp = open(filename, u'rb')
+            fp = open(filename, r'rb')
         except IOError:
             if not sections: # ignore unless we were looking for something
                 return