diff -r 517ffec37dee -r a3fcc8e3136b mercurial/context.py
--- a/mercurial/context.py	Mon Oct 12 00:45:24 2015 -0700
+++ b/mercurial/context.py	Fri Oct 09 01:19:37 2015 +0200
@@ -5,6 +5,8 @@
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
+import re
+
 from node import nullid, nullrev, wdirid, short, hex, bin
 from i18n import _
 import mdiff, error, util, scmutil, subrepo, patch, encoding, phases
@@ -22,6 +24,8 @@
 # dirty in the working copy.
 _newnode = '!' * 21
 
+nonascii = re.compile(r'[^\x21-\x7f]').search
+
 class basectx(object):
     """A basectx object represents the common logic for its children:
     changectx: read-only context that is already present in the repo,
@@ -466,7 +470,7 @@
                 msg = _("working directory has unknown parent '%s'!")
                 raise error.Abort(msg % short(changeid))
             try:
-                if len(changeid) == 20:
+                if len(changeid) == 20 and nonascii(changeid):
                     changeid = hex(changeid)
             except TypeError:
                 pass