mercurial/phases.py

--- a/mercurial/phases.py	Sat Nov 09 13:23:51 2019 +0100
+++ b/mercurial/phases.py	Sat Nov 09 13:23:52 2019 +0100
@@ -733,7 +733,7 @@
 
     repo = repo.unfiltered()
     cl = repo.changelog
-    rev = cl.nodemap.get
+    rev = cl.index.get_rev
     if not roots:
         return heads
     if not heads or heads == [nullid]: