--- a/mercurial/setdiscovery.py	Thu Nov 22 15:14:24 2018 +0300
+++ b/mercurial/setdiscovery.py	Thu Mar 14 19:13:45 2019 +0000
@@ -169,7 +169,7 @@
     def _parentsgetter(self):
         getrev = self._repo.changelog.index.__getitem__
         def getparents(r):
-            return getrev(r)[5:6]
+            return getrev(r)[5:7]
         return getparents
 
     def _childrengetter(self):