diff --git a/sys/netinet6/ip6_output.c b/sys/netinet6/ip6_output.c
index 1fdedf1eea7e..df5ec0fe6d2a 100644
--- a/sys/netinet6/ip6_output.c
+++ b/sys/netinet6/ip6_output.c
@@ -1615,18 +1615,22 @@ ip6_ctloutput(struct socket *so, struct sockopt *sopt)
 					break;
 #define OPTSET(bit) \
 do { \
+	INP_WLOCK(in6p); \
 	if (optval) \
 		in6p->inp_flags |= (bit); \
 	else \
 		in6p->inp_flags &= ~(bit); \
+	INP_WUNLOCK(in6p); \
 } while (/*CONSTCOND*/ 0)
 #define OPTSET2292(bit) \
 do { \
+	INP_WLOCK(in6p); \
 	in6p->inp_flags |= IN6P_RFC2292; \
 	if (optval) \
 		in6p->inp_flags |= (bit); \
 	else \
 		in6p->inp_flags &= ~(bit); \
+	INP_WUNLOCK(in6p); \
 } while (/*CONSTCOND*/ 0)
 #define OPTBIT(bit) (in6p->inp_flags & (bit) ? 1 : 0)
 
@@ -1880,6 +1884,7 @@ do { \
 				if (error)
 					break;
 
+				INP_WLOCK(in6p);
 				switch (optval) {
 				case IPV6_PORTRANGE_DEFAULT:
 					in6p->inp_flags &= ~(INP_LOWPORT);
@@ -1900,6 +1905,7 @@ do { \
 					error = EINVAL;
 					break;
 				}
+				INP_WUNLOCK(in6p);
 				break;
 
 #ifdef IPSEC