diff --git a/hgext/convert/common.py b/hgext/convert/common.py
--- a/hgext/convert/common.py
+++ b/hgext/convert/common.py
@@ -2,7 +2,7 @@
 import base64, errno
 import os
 import cPickle as pickle
-from mercurial import util
+from mercurial import util, strutil
 from mercurial.i18n import _
 
 def encodeargs(args):
@@ -334,7 +334,7 @@ class mapfile(dict):
                 raise
             return
         for line in fp:
-            key, value = line[:-1].split(' ', 1)
+            key, value = strutil.rsplit(line[:-1], ' ', 1)
             if key not in self:
                 self.order.append(key)
             super(mapfile, self).__setitem__(key, value)
diff --git a/mercurial/strutil.py b/mercurial/strutil.py
--- a/mercurial/strutil.py
+++ b/mercurial/strutil.py
@@ -32,3 +32,10 @@ def rfindall(haystack, needle, start=0, 
             break
         yield c
         end = c - 1
+
+def rsplit(s, sep=None, maxsplit=-1):
+    try:
+        return s.rsplit(sep, maxsplit)
+    except AttributeError:
+        return  [chunk[::-1] for chunk in 
+                 s[::-1].split(sep, maxsplit)[::-1]]