--- a/hgext3rd/serverminitopic.py	Fri Apr 12 02:20:24 2019 +0200
+++ b/hgext3rd/serverminitopic.py	Wed Apr 17 16:18:22 2019 +0800
@@ -159,8 +159,13 @@
 
     def copy(self):
         """return an deep copy of the branchcache object"""
-        new = self.__class__(self, self.tipnode, self.tiprev, self.filteredhash,
-                             self._closednodes)
+        if util.safehasattr(self, '_entries'):
+            _entries = self._entries
+        else:
+            # hg <= 4.9 (624d6683c705, b137a6793c51)
+            _entries = self
+        new = self.__class__(_entries, self.tipnode, self.tiprev,
+                             self.filteredhash, self._closednodes)
         new.phaseshash = self.phaseshash
         return new