diff -r 7c9d4cf23adf -r be5eeaf5c24a mercurial/branchmap.py
--- a/mercurial/branchmap.py	Fri Apr 05 15:56:33 2019 +0300
+++ b/mercurial/branchmap.py	Fri Apr 05 15:57:09 2019 +0300
@@ -304,7 +304,6 @@
         otherwise return last closed head and true.'''
         tip = heads[-1]
         closed = True
-        self._verifyclosed()
         for h in reversed(heads):
             if h not in self._closednodes:
                 tip = h