diff -r 45d123d84011 -r a49b2e253035 mercurial/exchange.py
--- a/mercurial/exchange.py	Sat Nov 09 13:23:53 2019 +0100
+++ b/mercurial/exchange.py	Sat Nov 09 13:23:53 2019 +0100
@@ -528,8 +528,8 @@
         # We can pick:
         # * missingheads part of common (::commonheads)
         common = self.outgoing.common
-        nm = self.repo.changelog.nodemap
-        cheads = [node for node in self.revs if nm[node] in common]
+        rev = self.repo.changelog.index.rev
+        cheads = [node for node in self.revs if rev(node) in common]
         # and
         # * commonheads parents on missing
         revset = unfi.set(