popsu-d7/sites/all/modules/jquery_update/js/jquery_update.js

(function (D) {
  var beforeSerialize = D.ajax.prototype.beforeSerialize;
  D.ajax.prototype.beforeSerialize = function (element, options) {
    beforeSerialize.call(this, element, options);
    options.data['ajax_page_state[jquery_version]'] = D.settings.ajaxPageState.jquery_version;
  }
})(Drupal);