diff -r dffc35a5be9f -r 8a0cac20a1ad mercurial/debugcommands.py
--- a/mercurial/debugcommands.py	Sat Dec 09 14:22:12 2017 -0800
+++ b/mercurial/debugcommands.py	Mon Dec 11 09:27:40 2017 -0800
@@ -225,7 +225,8 @@
 
                 def fctxfn(repo, cx, path):
                     if path in filecontent:
-                        return context.memfilectx(repo, path, filecontent[path])
+                        return context.memfilectx(repo, cx, path,
+                                                  filecontent[path])
                     return None
 
                 if len(ps) == 0 or ps[0] < 0: