diff -r 2133437dad17 -r f424fb180fea mercurial/revlog.py
--- a/mercurial/revlog.py	Thu Mar 30 15:34:08 2017 -0700
+++ b/mercurial/revlog.py	Thu Mar 30 17:58:03 2017 -0700
@@ -1635,7 +1635,7 @@
                         fh = ifh
                     else:
                         fh = dfh
-                    ptext = self.revision(rev, _df=fh)
+                    ptext = self.revision(rev, _df=fh, raw=True)
                     delta = mdiff.textdiff(ptext, t)
             header, data = self.compress(delta)
             deltalen = len(header) + len(data)