diff -r baf58e621363 -r 8e1386b342f7 mercurial/context.py
--- a/mercurial/context.py	Thu Dec 07 16:07:06 2017 -0800
+++ b/mercurial/context.py	Thu Dec 07 16:07:06 2017 -0800
@@ -1976,9 +1976,9 @@
     def setflags(self, l, x):
         self._repo.wvfs.setflags(self._path, l, x)
 
-class overlayworkingctx(workingctx):
-    """Wraps another mutable context with a write-back cache that can be flushed
-    at a later time.
+class overlayworkingctx(committablectx):
+    """Wraps another mutable context with a write-back cache that can be
+    converted into a commit context.
 
     self._cache[path] maps to a dict with keys: {
         'exists': bool?
@@ -2161,7 +2161,7 @@
         return overlayworkingfilectx(self._repo, path, parent=self,
                                      filelog=filelog)
 
-class overlayworkingfilectx(workingfilectx):
+class overlayworkingfilectx(committablefilectx):
     """Wrap a ``workingfilectx`` but intercepts all writes into an in-memory
     cache, which can be flushed through later by calling ``flush()``."""