Index: sys/netpfil/ipfw/nat64/nat64clat.c
===================================================================
--- sys/netpfil/ipfw/nat64/nat64clat.c
+++ sys/netpfil/ipfw/nat64/nat64clat.c
@@ -102,6 +102,11 @@
 	nat64_embed_ip4(&saddr, cfg->base.clat_plen, ip->ip_src.s_addr);
 	memcpy(&daddr, &cfg->base.plat_prefix, sizeof(daddr));
 	nat64_embed_ip4(&daddr, cfg->base.plat_plen, ip->ip_dst.s_addr);
+	if (m->m_pkthdr.rcvif == NULL &&
+		m->m_pkthdr.csum_flags & CSUM_DELAY_DATA) {
+			in_delayed_cksum(m);
+			m->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA;
+	}
 	if (cfg->base.flags & NAT64_LOG) {
 		logdata = &loghdr;
 		nat64clat_log(logdata, m, AF_INET, cfg->no.kidx);