diff --git a/mercurial/mergestate.py b/mercurial/mergestate.py
--- a/mercurial/mergestate.py
+++ b/mercurial/mergestate.py
@@ -10,7 +10,6 @@
     bin,
     hex,
     nullhex,
-    nullid,
     nullrev,
 )
 from . import (