Index: head/sys/kern/kern_event.c
===================================================================
--- head/sys/kern/kern_event.c
+++ head/sys/kern/kern_event.c
@@ -1116,6 +1116,9 @@
 	int error, filt, event;
 	int haskqglobal, filedesc_unlock;
 
+	if ((kev->flags & (EV_ENABLE | EV_DISABLE)) == (EV_ENABLE | EV_DISABLE))
+		return (EINVAL);
+
 	fp = NULL;
 	kn = NULL;
 	error = 0;