diff -r 53581e220ba3 -r 642433629e20 mercurial/unionrepo.py
--- a/mercurial/unionrepo.py	Fri Nov 08 10:01:10 2019 +0100
+++ b/mercurial/unionrepo.py	Sat Nov 09 05:54:22 2019 +0100
@@ -83,7 +83,6 @@
                 node,
             )
             self.index.append(e)
-            self.nodemap[node] = n
             self.bundlerevs.add(n)
             n += 1