diff --git a/mercurial/mergestate.py b/mercurial/mergestate.py
--- a/mercurial/mergestate.py
+++ b/mercurial/mergestate.py
@@ -382,7 +382,6 @@
         if merge_ret is None:
             # If return value of merge is None, then there are no real conflict
             del self._state[dfile]
-            self._stateextras.pop(dfile, None)
             self._dirty = True
         elif not merge_ret:
             self.mark(dfile, MERGE_RECORD_RESOLVED)