diff --git a/net/altq/altq_rmclass.c b/net/altq/altq_rmclass.c
--- a/net/altq/altq_rmclass.c
+++ b/net/altq/altq_rmclass.c
@@ -198,7 +198,7 @@
 	struct rm_class *cl;
 	struct rm_class *peer;
 
-	if (pri >= RM_MAXPRIO)
+	if (pri < 0 || pri >= RM_MAXPRIO)
 		return (NULL);
 #ifndef ALTQ_RED
 	if (flags & RMCF_RED) {