Cannot access facebook data through chrome extension

Question

I've so far suceeded in getting a valid access token. Now I'm just trying to get a JSON response using jQuery.

This is most of my code. It is called on load from a window created by the background.html:

$.ajax({
    url : 'https://graph.facebook.com/me?access_token=' + access_token,
    dataType: 'json',
    error: function() { alert('error'); },
    success: function( data ) { 
        alert( data );
    },
    type: 'GET'
}); 

The result is an alert with "NULL" as text.

The exact same url works fine if I paste it directly into my browser. Then I get my userdata back as expected.

What am i doing wrong?