diff --git a/sys/netinet/tcp_subr.c b/sys/netinet/tcp_subr.c
index b2f34c1b806..f8b07072ad0 100644
--- a/sys/netinet/tcp_subr.c
+++ b/sys/netinet/tcp_subr.c
@@ -1170,10 +1170,11 @@ tcp_ctlinput(cmd, sa, vip)
 					    /*
 					     * If no alternative MTU was
 					     * proposed, try the next smaller
-					     * one.
+					     * one.  ip->ip_len has already
+					     * been swapped in icmp_input().
 					     */
 					    if (!mtu)
-						mtu = ip_next_mtu(ntohs(ip->ip_len),
+						mtu = ip_next_mtu(ip->ip_len,
 						 1);
 					    if (mtu < max(296, (tcp_minmss)
 						 + sizeof(struct tcpiphdr)))
diff --git a/sys/netinet/tcp_timewait.c b/sys/netinet/tcp_timewait.c
index b2f34c1b806..f8b07072ad0 100644
--- a/sys/netinet/tcp_timewait.c
+++ b/sys/netinet/tcp_timewait.c
@@ -1170,10 +1170,11 @@ tcp_ctlinput(cmd, sa, vip)
 					    /*
 					     * If no alternative MTU was
 					     * proposed, try the next smaller
-					     * one.
+					     * one.  ip->ip_len has already
+					     * been swapped in icmp_input().
 					     */
 					    if (!mtu)
-						mtu = ip_next_mtu(ntohs(ip->ip_len),
+						mtu = ip_next_mtu(ip->ip_len,
 						 1);
 					    if (mtu < max(296, (tcp_minmss)
 						 + sizeof(struct tcpiphdr)))