diff -r a362b0b95e42 -r b26455ffa7fa mercurial/branchmap.py
--- a/mercurial/branchmap.py	Fri Apr 05 14:35:33 2019 +0200
+++ b/mercurial/branchmap.py	Tue Apr 16 14:39:14 2019 +0300
@@ -339,7 +339,6 @@
 
     def copy(self):
         """return an deep copy of the branchcache object"""
-        self._verifyall()
         return type(self)(
             self._entries, self.tipnode, self.tiprev, self.filteredhash,
             self._closednodes)