Calling .accordion("activate", false) fires changestart event with incorrect values

Example code:

$("#element").accordion({
  active: false,
  collapsible: true,
  changestart: function(event, ui) {
    // When I later call $("#element").accordion("activate", false), this event gets fired,
    // and the value for ui.oldHeader right here is false, even if there was an activated
    // row prior to the call.
  }
});