jquery Sortable connectWith calls the update method twice

Question

In the code below the update function gets called twice when an item is moved from list sortable1 to sortable2. Though I need to call that function only once:

$("#sortable1 tbody, #sortable2 tbody").sortable({
    connectWith: '.connectedSortable tbody',
    helper: fixHelper,
    handle : '.handle',
    update : function () {
        var order = $('#sortable1 tbody').sortable('serialize');
    }    
}).disableSelection();

Answer 1

Answer from: http://forum.jquery.com/topic/sortables-update-callback-and-connectwith

update: function(e,ui) {
    if (this === ui.item.parent()[0]) {
        //your code here
    }
}