Adding a request header on beforeSend

Im using storageManager remote but the site has csrf token

    beforeSend: function (t) {
        var token = $('meta[name="csrf_token"]').attr('content');
                        if (token) {
                            return t.setRequestHeader('X-CSRF-TOKEN', token);
                        }
         },

Gives an error "Uncaught TypeError: Cannot read property 'setRequestHeader' of undefined"
obviously because t is undefined, how can I pass the headers into beforeSend without changing grapesjs