mercurial/context.py

--- a/mercurial/context.py	Fri May 10 10:23:46 2019 -0700
+++ b/mercurial/context.py	Fri May 10 14:27:22 2019 -0700
@@ -2055,7 +2055,7 @@
         else:
             parents = (self._repo[parents[0]], self._repo[parents[1]])
 
-        files = self._cache.keys()
+        files = self.files()
         def getfile(repo, memctx, path):
             if self._cache[path]['exists']:
                 return memfilectx(repo, memctx, path,