--- cci/sys/netinet/tcp_subr.c	2019/07/28 12:24:19	1.1
+++ cci/sys/netinet/tcp_subr.c	2019/07/28 12:29:37	1.1.1.2
@@ -110,12 +110,20 @@ tcp_respond(tp, ti, ack, seq, flags)
 		ro = &tp->t_inpcb->inp_route;
 	}
 	if (flags == 0) {
+#if defined(tahoe)
+		register struct tcpiphdr *x;	/* work around compiler bug */
+#endif
 		m = m_get(M_DONTWAIT, MT_HEADER);
 		MBUFNULL(15, m);		/* for debugging */
 		if (m == NULL)
 			return;
 		m->m_len = sizeof (struct tcpiphdr) + 1;
+#if defined(tahoe)
+		x = mtod(m, struct tcpiphdr *);
+		*x = *ti;
+#else
 		*mtod(m, struct tcpiphdr *) = *ti;
+#endif
 		ti = mtod(m, struct tcpiphdr *);
 		flags = TH_ACK;
 		tlen = 1;