$.ajaxSetup({timeout:15000}); does not seem to work with jQuery.getJSON. What am I doing wrong?

$.ajaxSetup({timeout:15000}); does not seem to work with jQuery.getJSON. What am I doing wrong?

My code is:

function logInJS(fields, dv) { // VARs defined here are visible in callback
  var elem = document.getElementById(fields);
  var dvD = dv;
  $.ajaxSetup({timeout:15000}); // milliseconds of timeout
  jQuery.getJSON(baseURL + 'json?verb=6', $(elem).serialize(),
function(data, status, xhr) {
  if (data.msg)  {
    alert(data.msg);
  } else {

This works fine when the server is running.  Status is "success" and xhr.status is 200 as expected.  When I turn the server off so that there will never be a reply, however, the timeout doesn't seem to fire.  

As I read the documentation, this was supposed to set a timeout for all ajax calls and getJSON was supposed to create an ajax call eventually.  What am I missing?

Thank you