Index: head/sys/net/pfvar.h
===================================================================
--- head/sys/net/pfvar.h
+++ head/sys/net/pfvar.h
@@ -824,6 +824,7 @@
 typedef	void		pfsync_delete_state_t(struct pf_state *);
 typedef void		pfsync_clear_states_t(u_int32_t, const char *);
 typedef int		pfsync_defer_t(struct pf_state *, struct mbuf *);
+typedef void		pfsync_detach_ifnet_t(struct ifnet *);
 
 VNET_DECLARE(pfsync_state_import_t *, pfsync_state_import_ptr);
 #define V_pfsync_state_import_ptr	VNET(pfsync_state_import_ptr)
@@ -837,6 +838,7 @@
 #define V_pfsync_clear_states_ptr	VNET(pfsync_clear_states_ptr)
 VNET_DECLARE(pfsync_defer_t *, pfsync_defer_ptr);
 #define V_pfsync_defer_ptr		VNET(pfsync_defer_ptr)
+extern pfsync_detach_ifnet_t	*pfsync_detach_ifnet_ptr;
 
 void			pfsync_state_export(struct pfsync_state *,
 			    struct pf_state *);
Index: head/sys/netpfil/pf/if_pfsync.c
===================================================================
--- head/sys/netpfil/pf/if_pfsync.c
+++ head/sys/netpfil/pf/if_pfsync.c
@@ -281,6 +281,7 @@
 static void	pfsync_bulk_update(void *);
 static void	pfsync_bulk_fail(void *);
 
+static void	pfsync_detach_ifnet(struct ifnet *);
 #ifdef IPSEC
 static void	pfsync_update_net_tdb(struct pfsync_tdb *);
 #endif
@@ -2292,6 +2293,29 @@
 	imo->imo_multicast_ifp = NULL;
 }
 
+void
+pfsync_detach_ifnet(struct ifnet *ifp)
+{
+	struct pfsync_softc *sc = V_pfsyncif;
+
+	if (sc == NULL)
+		return;
+
+	PFSYNC_LOCK(sc);
+
+	if (sc->sc_sync_if == ifp) {
+		/* We don't need mutlicast cleanup here, because the interface
+		 * is going away. We do need to ensure we don't try to do
+		 * cleanup later.
+		 */
+		sc->sc_imo.imo_membership = NULL;
+		sc->sc_imo.imo_multicast_ifp = NULL;
+		sc->sc_sync_if = NULL;
+	}
+
+	PFSYNC_UNLOCK(sc);
+}
+
 #ifdef INET
 extern  struct domain inetdomain;
 static struct protosw in_pfsync_protosw = {
@@ -2372,6 +2396,8 @@
 #ifdef INET
 	int error;
 
+	pfsync_detach_ifnet_ptr = pfsync_detach_ifnet;
+
 	error = pf_proto_register(PF_INET, &in_pfsync_protosw);
 	if (error)
 		return (error);
@@ -2388,6 +2414,7 @@
 static void
 pfsync_uninit()
 {
+	pfsync_detach_ifnet_ptr = NULL;
 
 #ifdef INET
 	ipproto_unregister(IPPROTO_PFSYNC);
Index: head/sys/netpfil/pf/pf_if.c
===================================================================
--- head/sys/netpfil/pf/pf_if.c
+++ head/sys/netpfil/pf/pf_if.c
@@ -834,6 +834,9 @@
 {
 	struct pfi_kif *kif = (struct pfi_kif *)ifp->if_pf_kif;
 
+	if (pfsync_detach_ifnet_ptr)
+		pfsync_detach_ifnet_ptr(ifp);
+
 	if (kif == NULL)
 		return;
 
@@ -841,6 +844,7 @@
 		/* Avoid teardown race in the least expensive way. */
 		return;
 	}
+
 	PF_RULES_WLOCK();
 	V_pfi_update++;
 	pfi_kif_update(kif);
Index: head/sys/netpfil/pf/pf_ioctl.c
===================================================================
--- head/sys/netpfil/pf/pf_ioctl.c
+++ head/sys/netpfil/pf/pf_ioctl.c
@@ -218,6 +218,7 @@
 VNET_DEFINE(pfsync_delete_state_t *, pfsync_delete_state_ptr);
 VNET_DEFINE(pfsync_clear_states_t *, pfsync_clear_states_ptr);
 VNET_DEFINE(pfsync_defer_t *, pfsync_defer_ptr);
+pfsync_detach_ifnet_t *pfsync_detach_ifnet_ptr;
 
 /* pflog */
 pflog_packet_t			*pflog_packet_ptr = NULL;