diff --git a/contrib/pg_upgrade/pg_upgrade.c b/contrib/pg_upgrade/pg_upgrade.c
index 42da3ea0df..331ade1076 100644
--- a/contrib/pg_upgrade/pg_upgrade.c
+++ b/contrib/pg_upgrade/pg_upgrade.c
@@ -28,6 +28,9 @@
  *
  *	We control all assignments of pg_enum.oid because these oids are stored
  *	in user tables as enum values.
+ *
+ *	We control all assignments of pg_auth.oid because these oids are stored
+ *	in pg_largeobject_metadata.
  */