diff --git a/sys/netinet6/udp6_usrreq.c b/sys/netinet6/udp6_usrreq.c
index 53439d0f3cb3..8617d0d39c53 100644
--- a/sys/netinet6/udp6_usrreq.c
+++ b/sys/netinet6/udp6_usrreq.c
@@ -538,6 +538,8 @@ udp6_attach(struct socket *so, int proto, struct thread *td)
 		return error;
 	inp = (struct inpcb *)so->so_pcb;
 	inp->inp_vflag |= INP_IPV6;
+	if (ip6_mapped_addr_on)
+		inp->inp_vflag |= INP_IPV4;
 	inp->in6p_hops = -1;	/* use kernel default */
 	inp->in6p_cksum = -1;	/* just to be sure */
 	/*