diff -up shadow-4.6/src/useradd.c.useradd-check-if-subid-range-exists shadow-4.6/src/useradd.c
--- shadow-4.6/src/useradd.c.useradd-check-if-subid-range-exists	2023-05-17 10:39:41.457826153 +0200
+++ shadow-4.6/src/useradd.c	2023-05-17 10:41:30.937036772 +0200
@@ -2019,14 +2019,14 @@ static void usr_update (void)
 		fail_exit (E_PW_UPDATE);
 	}
 #ifdef ENABLE_SUBIDS
-	if (is_sub_uid &&
+	if (is_sub_uid && !local_sub_uid_assigned(user_name) &&
 	    (sub_uid_add(user_name, sub_uid_start, sub_uid_count) == 0)) {
 		fprintf (stderr,
 		         _("%s: failed to prepare the new %s entry\n"),
 		         Prog, sub_uid_dbname ());
 		fail_exit (E_SUB_UID_UPDATE);
 	}
-	if (is_sub_gid &&
+	if (is_sub_gid && !local_sub_gid_assigned(user_name) &&
 	    (sub_gid_add(user_name, sub_gid_start, sub_gid_count) == 0)) {
 		fprintf (stderr,
 		         _("%s: failed to prepare the new %s entry\n"),