diff --git a/libs/sofia-sip/libsofia-sip-ua/nta/nta.c b/libs/sofia-sip/libsofia-sip-ua/nta/nta.c
index 5e5fa2ca9e..3bd34df648 100644
--- a/libs/sofia-sip/libsofia-sip-ua/nta/nta.c
+++ b/libs/sofia-sip/libsofia-sip-ua/nta/nta.c
@@ -2398,7 +2398,7 @@ void agent_recv_request(nta_agent_t *agent,
   else if (!agent->sa_is_stateless && (leg = agent->sa_default_leg)) {
 	if (method == sip_method_invite && agent->sa_in.proceeding->q_length >= agent->sa_max_proceeding) {
 		SU_DEBUG_5(("nta: proceeding queue full for %s (%u)\n", method_name, cseq));
-		nta_msg_treply(agent, msg, SIP_486_BUSY_HERE,
+		nta_msg_treply(agent, msg, SIP_503_SERVICE_UNAVAILABLE,
 			   NTATAG_TPORT(tport), 
 			   TAG_END());
 		return;
diff --git a/src/mod/endpoints/mod_sofia/sofia.c b/src/mod/endpoints/mod_sofia/sofia.c
index f48e288b2d..d2d31ec667 100644
--- a/src/mod/endpoints/mod_sofia/sofia.c
+++ b/src/mod/endpoints/mod_sofia/sofia.c
@@ -1885,7 +1885,7 @@ void sofia_handle_sip_i_invite(nua_t *nua, sofia_profile_t *profile, nua_handle_
 	}
 	
 	if (!sofia_endpoint_interface || !(session = switch_core_session_request(sofia_endpoint_interface, NULL))) {
-		nua_respond(nh, SIP_486_BUSY_HERE, TAG_END());
+		nua_respond(nh, SIP_503_SERVICE_UNAVAILABLE, TAG_END());
 		return;
 	}