Index: mercurial/context.py
===================================================================
--- mercurial/context.py
+++ mercurial/context.py
@@ -1976,8 +1976,8 @@
     def __init__(self, repo, wrappedctx):
         super(overlayworkingctx, self).__init__(repo)
         self._repo = repo
+        self.clean()
         self._wrappedctx = wrappedctx
-        self._clean()
 
     def data(self, path):
         if self.isdirty(path):
@@ -2057,7 +2057,7 @@
     def isdirty(self, path):
         return path in self._cache
 
-    def _clean(self):
+    def clean(self):
         self._cache = {}
         self._writeorder = []