--- a/sys/net/altq/altq_fairq.c	2026-06-29 12:51:19.000000000 +0000
+++ b/sys/net/altq/altq_fairq.c	2026-10-26 03:31:47.247168419 +0000
@@ -227,7 +227,7 @@
 	int error;
 
 	/* check parameters */
-	if (a->priority >= FAIRQ_MAXPRI)
+	if (a->priority < 0 || a->priority >= FAIRQ_MAXPRI)
 		return (EINVAL);
 	if (a->qid == 0)
 		return (EINVAL);