how to add Headers when connect to websocket?

[k...@noosh.com]

we set up websocket topic with Spring websocket, and then the client side is using Stomp.js to subscribe it;
it works fine if connect to the websocket service directly; but now we set up Kong as the API Gateway in front of the websocket service; it needs to set header "Host: websocket.com" when connect to it;
But it doesn't work with Stomp.js;

    var url='http://xx.xx.xx.xx:8000/websocket/tracker';
    var socket = new SockJS(url);
    stompClient = Stomp.over(socket);
    var thisheaders={
            Host:'websocket.com'
    };
    stompClient.connect(thisheaders, function (frame) {
        setConnected(true);
        console.log('Connected: ' + frame);
        stompClient.subscribe('/topic/greetings', function (greeting) {
            showGreeting(JSON.parse(greeting.body).content);
        });
    });

Does anyone know how to add the headers for it? Or the Stomp.js just doesn't support to add headers? 

Thanks!