diff --git a/includes/dhcp6.h b/includes/dhcp6.h
index bf8205c..e2258f1 100644
--- a/includes/dhcp6.h
+++ b/includes/dhcp6.h
@@ -115,6 +115,7 @@
 #define D6O_V6_PCP_SERVER			86 /* RFC7291 */
 #define D6O_DHCPV4_MSG				87 /* RFC7341 */
 #define D6O_DHCP4_O_DHCP6_SERVER		88 /* RFC7341 */
+#define D6O_RELAY_PORT                          90 /* XXX draft relay-port */
 
 /* 
  * Status Codes, from RFC 3315 section 24.4, and RFC 3633, 5007, 5460.
diff --git a/includes/dhcpd.h b/includes/dhcpd.h
index 261714d..05a5c12 100644
--- a/includes/dhcpd.h
+++ b/includes/dhcpd.h
@@ -472,6 +472,9 @@ struct packet {
 	/* Propogates server value SV_ECHO_CLIENT_ID so it is available
          * in cons_options() */
 	int sv_echo_client_id;
+
+	/* Relay port check */
+	isc_boolean_t relay_source_port;
 };
 
 /*
@@ -2788,6 +2791,7 @@ extern struct in_addr local_address;
 
 extern u_int16_t local_port;
 extern u_int16_t remote_port;
+extern u_int16_t relay_port;
 extern int dhcpv4_over_dhcpv6;
 extern int (*dhcp_interface_setup_hook) (struct interface_info *,
 					 struct iaddr *);
diff --git a/server/dhcpv6.c b/server/dhcpv6.c
index 18d8bb8..4b8a41c 100644
--- a/server/dhcpv6.c
+++ b/server/dhcpv6.c
@@ -844,6 +844,7 @@ static const int required_opts_solicit[] = {
 };
 static const int required_opts_agent[] = {
 	D6O_INTERFACE_ID,
+	D6O_RELAY_PORT,
 	D6O_RELAY_MSG,
 	0
 };
@@ -6545,6 +6546,33 @@ dhcpv6_relay_forw(struct data_string *reply_ret, struct packet *packet) {
 	}
 
 	/*
+	 * Append the relay_port option if present.
+	 */
+	oc = lookup_option(&dhcpv6_universe, packet->options,
+			   D6O_RELAY_PORT);
+	if (oc != NULL) {
+		if (!evaluate_option_cache(&a_opt, packet,
+					   NULL, NULL,
+					   packet->options, NULL,
+					   &global_scope, oc, MDL)) {
+			log_error("dhcpv6_relay_forw: error evaluating "
+				  "Relay Port.");
+			goto exit;
+		}
+		if (!save_option_buffer(&dhcpv6_universe, opt_state, NULL,
+					(unsigned char *)a_opt.data,
+					a_opt.len,
+					D6O_RELAY_PORT, 0)) {
+			log_error("dhcpv6_relay_forw: error saving "
+				  "Relay Port.");
+			goto exit;
+		}
+		data_string_forget(&a_opt, MDL);
+
+		packet->relay_source_port = ISC_TRUE;
+	}
+
+	/*
 	 * Append our encapsulated stuff for caller.
 	 */
 	if (!save_option_buffer(&dhcpv6_universe, opt_state, NULL,
@@ -7379,6 +7407,10 @@ dhcpv6(struct packet *packet) {
 		 */
 		to_addr.sin6_port = packet->client_port;
 #endif
+		/* Check relay source port */
+		if (packet->relay_source_port && packet->client_port != 547) {
+			to_addr.sin6_port = packet->client_port;
+		}
 
 		memcpy(&to_addr.sin6_addr, packet->client_addr.iabuf,
 		       sizeof(to_addr.sin6_addr));