--- kern_event.c.orig	2007-07-14 14:23:30.000000000 -0700
+++ kern_event.c	2008-03-02 16:26:59.000000000 -0800
@@ -1590,6 +1590,8 @@
 	KQ_NOTOWNED(kn->kn_kq);
 	KASSERT((kn->kn_status & (KN_INFLUX|KN_DETACHED)) ==
 	    (KN_INFLUX|KN_DETACHED), ("knote not KN_INFLUX and KN_DETACHED"));
+	KASSERT((kn->kn_status & (KN_MARKER)) == 0,
+	    ("knote has KN_MARKER set"));
 	if (!islocked)
 		knl->kl_lock(knl->kl_lockarg);
 	SLIST_INSERT_HEAD(&knl->kl_list, kn, kn_selnext);