--- a/mercurial/metadata.py	Mon Apr 19 20:38:52 2021 -0400
+++ b/mercurial/metadata.py	Mon Mar 29 01:52:06 2021 +0200
@@ -11,10 +11,7 @@
 import multiprocessing
 import struct
 
-from .node import (
-    nullid,
-    nullrev,
-)
+from .node import nullrev
 from . import (
     error,
     pycompat,
@@ -617,7 +614,7 @@
         if f in ctx:
             fctx = ctx[f]
             parents = fctx._filelog.parents(fctx._filenode)
-            if parents[1] != nullid:
+            if parents[1] != ctx.repo().nullid:
                 merged.append(f)
     return merged