Serving compressed API response

[Yash Ganthe]

I have this in my app.js:

app.configure(function() {
    app.use(express.cookieParser());
    app.use(express.bodyParser());
    app.use(express.session({
        secret: 'supersecretkeygoeshere',
        store: new MySQLStore(options),
        //cookie: {maxAge: 1000}
    }));
    app.use(passport.initialize());
    app.use(passport.session());   

    app.set('views', path.join(__dirname, 'public'));

    app.use(express.favicon());


    app.use(express.json());
    app.use(express.urlencoded());
    app.use(express.methodOverride());
    app.use(app.router);
    app.use(express.compress());

Apart from serving static files, I serve an API such as:

app.get('/api/myfun', function(req, res) {
    res.json('Lot of data');
});

The static files get served with Content-Encoding property value as gzip. When I observe the reponse of the API in the browser, the Content-Encoding property is not "gzip". What do I need to do so that the API is also served in gzip format?