I have got the following very simple code:
function init() {
    var articleTabs = $('#articleTabs');
    articleTabs.tabs('add',
            admin.pageVars.siteRoot + '/articles/themes/' + admin.pageVars.params.id, 'Temas');
    articleTabs.tabs({
        load : function(event, ui) {
            $('.jsonForm').jsonForm();
        }
    });
}
This successfully adds a new tab panel to an existing tab control. However upon activation, the load function does never fire.
What is my mistake? (There are no javascript exceptions)