diff --git a/mercurial/context.py b/mercurial/context.py
--- a/mercurial/context.py
+++ b/mercurial/context.py
@@ -2160,7 +2160,7 @@
     def cmp(self, fctx):
         return self.data() != fctx.data()
 
-    def ctx(self):
+    def changectx(self):
         return self._parent
 
     def data(self):
diff --git a/mercurial/filemerge.py b/mercurial/filemerge.py
--- a/mercurial/filemerge.py
+++ b/mercurial/filemerge.py
@@ -481,7 +481,7 @@
     # calls might be depending on.
     from . import context
     if isinstance(fcd, context.overlayworkingfilectx):
-        fcd.ctx().flushall()
+        fcd.changectx().flushall()
 
     util.writefile(a + ".local", fcd.decodeddata())
     repo.wwrite(fd + ".other", fco.data(), fco.flags())