diff --git a/res/res_pjsip_outbound_publish.c b/res/res_pjsip_outbound_publish.c
index 53e15a0..70350b2 100644
--- a/res/res_pjsip_outbound_publish.c
+++ b/res/res_pjsip_outbound_publish.c
@@ -813,6 +813,8 @@ static int publisher_client_send(void *obj, void *arg, void *data, int flags)
                message->body.body_text = strcpy(dst, body->body_text);
        }

+       SCOPED_AO2LOCK(lock, publisher);
+
        AST_LIST_INSERT_TAIL(&publisher->queue, message, entry);

        *res = ast_sip_push_task(NULL, sip_publisher_service_queue, ao2_bump(publisher));