--- a/mercurial/__init__.py	Sat Aug 13 12:12:50 2016 +0900
+++ b/mercurial/__init__.py	Sat Aug 13 12:15:49 2016 +0900
@@ -23,7 +23,6 @@
 # Modules that have both Python and C implementations. See also the
 # set of .py files under mercurial/pure/.
 _dualmodules = {
-    'mercurial.diffhelpers',
     'mercurial.mpatch',
     'mercurial.parsers',
 }