diff --git a/sys/kern/kern_sched.c b/sys/kern/kern_sched.c
--- a/sys/kern/kern_sched.c
+++ b/sys/kern/kern_sched.c
@@ -179,6 +179,11 @@
 		}
 		break;
 	case SCHED_OTHER:
+		if (param->sched_priority < P1B_PRIO_MIN ||
+			param->sched_priority > P1B_PRIO_MAX) {
+			e = EINVAL;
+			break;
+		}
 		rtp.type = RTP_PRIO_NORMAL;
 		rtp.prio = p4prio_to_rtpprio(param->sched_priority);
 		lp->lwp_rtprio = rtp;