--- a/mercurial/manifest.py	Mon Mar 30 15:38:24 2015 -0700
+++ b/mercurial/manifest.py	Tue Mar 10 09:57:42 2015 -0700
@@ -687,7 +687,7 @@
         return md
 
     def readdelta(self, node):
-        if self._usemanifestv2:
+        if self._usemanifestv2 or self._usetreemanifest:
             return self._slowreaddelta(node)
         r = self.rev(node)
         d = mdiff.patchtext(self.revdiff(self.deltaparent(r), r))