mercurial/context.py

--- a/mercurial/context.py	Wed Sep 14 17:12:39 2016 +0200
+++ b/mercurial/context.py	Tue Sep 13 16:25:21 2016 -0700
@@ -532,7 +532,8 @@
 
     @propertycache
     def _manifestdelta(self):
-        return self._repo.manifest.readdelta(self._changeset.manifest)
+        mfnode = self._changeset.manifest
+        return self._repo.manifestlog[mfnode].readdelta()
 
     @propertycache
     def _parents(self):