diff --git a/CHANGES b/CHANGES
index 6d2a8b87c8..99cd8aee32 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,5 @@
+4505.	[port]		Use IP_PMTUDISC_OMIT if available. [RT #35494]
+
 4504.	[security]	Allow the maximum number of records in a zone to
 			be specified.  This provides a control for issues
 			raised in CVE-2016-6170. [RT #42143]
diff --git a/lib/isc/unix/socket.c b/lib/isc/unix/socket.c
index 3f32161a2d..a4a4cd09b9 100644
--- a/lib/isc/unix/socket.c
+++ b/lib/isc/unix/socket.c
@@ -2858,11 +2858,24 @@ opensocket(isc__socketmgr_t *manager, isc__socket_t *sock,
 #if defined(IP_MTU_DISCOVER) && defined(IP_PMTUDISC_DONT)
 		/*
 		 * Turn off Path MTU discovery on IPv4/UDP sockets.
+		 * Prefer IP_PMTUDISC_OMIT over IP_PMTUDISC_DONT
+		 * if it available.
 		 */
 		if (sock->pf == AF_INET) {
-			int action = IP_PMTUDISC_DONT;
-			(void)setsockopt(sock->fd, IPPROTO_IP, IP_MTU_DISCOVER,
-					 &action, sizeof(action));
+			int action;
+#ifdef defined(IP_PMTUDISC_OMIT)
+			action = IP_PMTUDISC_OMIT;
+			if (setsockopt(sock->fd, IPPROTO_IPV6,
+					 IPV6_MTU_DISCOVER, &action,
+					 sizeof(action)) < 0) {
+#endif
+				action = IP_PMTUDISC_DONT;
+				(void)setsockopt(sock->fd, IPPROTO_IP,
+						 IP_MTU_DISCOVER,
+						 &action, sizeof(action));
+#ifdef defined(IP_PMTUDISC_OMIT)
+			}
+#endif
 		}
 #endif
 #if defined(IP_DONTFRAG)