Index: sys/netipsec/ipsec.c
===================================================================
--- sys/netipsec/ipsec.c
+++ sys/netipsec/ipsec.c
@@ -334,6 +334,12 @@
        IPSEC_ASSERT(dir == IPSEC_DIR_INBOUND || dir == IPSEC_DIR_OUTBOUND,
                ("invalid direction %u", dir));

+       if (!key_havesp(dir)) {
+               /* No SP found, use system default. */
+               sp = KEY_ALLOCSP_DEFAULT();
+               return (sp);
+       }
+
        /* Set spidx in pcb. */
        *error = ipsec_setspidx_inpcb(m, inp);
        if (*error)