diff --git a/sys/netinet6/udp6_usrreq.c b/sys/netinet6/udp6_usrreq.c
index abcac276ece..b42bc181720 100644
--- a/sys/netinet6/udp6_usrreq.c
+++ b/sys/netinet6/udp6_usrreq.c
@@ -647,6 +647,13 @@ udp6_attach(struct socket *so, int proto, struct proc *p)
 	inp->inp_vflag |= INP_IPV6;
 	inp->in6p_hops = -1;	/* use kernel default */
 	inp->in6p_cksum = -1;	/* just to be sure */
+	/*
+	 * XXX: ugly!!
+	 * IPv4 TTL initialization is necessary for an IPv6 socket as well,
+	 * because the socket may be bound to an IPv6 wildcard address,
+	 * which may match an IPv4-mapped IPv6 address.
+	 */
+	inp->inp_ip_ttl = ip_defttl;
 #ifdef IPSEC
 	error = ipsec_init_policy(so, &inp->in6p_sp);
 	if (error != 0) {