diff --git a/lib/libc/sys/kqueue.2 b/lib/libc/sys/kqueue.2
index b83d85d90d4..9be380bb5d9 100644
--- a/lib/libc/sys/kqueue.2
+++ b/lib/libc/sys/kqueue.2
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd October 8, 2020
+.Dd May 26, 2021
 .Dt KQUEUE 2
 .Os
 .Sh NAME
@@ -762,6 +762,8 @@ events were placed on the kqueue for return.
 A cancellation request was delivered to the thread, but not yet handled.
 .It Bq Er EINVAL
 The specified time limit or filter is invalid.
+.It Bq Er EINVAL
+The specified length of the event or change lists is negative.
 .It Bq Er ENOENT
 The event could not be found to be modified or deleted.
 .It Bq Er ENOMEM
diff --git a/sys/kern/kern_event.c b/sys/kern/kern_event.c
index e7047e9a7ad..b224ce87087 100644
--- a/sys/kern/kern_event.c
+++ b/sys/kern/kern_event.c
@@ -1303,6 +1303,9 @@ kqueue_kevent(struct kqueue *kq, struct thread *td, int nchanges, int nevents,
 	struct kevent *kevp, *changes;
 	int i, n, nerrors, error;
 
+	if (nchanges < 0)
+		return (EINVAL);
+
 	nerrors = 0;
 	while (nchanges > 0) {
 		n = nchanges > KQ_NEVENTS ? KQ_NEVENTS : nchanges;
@@ -1887,6 +1890,10 @@ kqueue_scan(struct kqueue *kq, int maxevents, struct kevent_copyops *k_ops,
 
 	if (maxevents == 0)
 		goto done_nl;
+	if (maxevents < 0) {
+		error = EINVAL;
+		goto done_nl;
+	}
 
 	rsbt = 0;
 	if (tsp != NULL) {