orderFixed post reorder failing to update class

orderFixed: {
    post: [1,'asc']
}

When you click on a column that has orderFixed on it, it will allow you to change it between asc and desc, but the icon to indicate which direction it is ordering on fails to update, instead constantly showing the order direction of the orderFixed, despite the data showing in the users altered direction.

See http://live.datatables.net/xigadiqi/1/edit for example

When clicking on the "Position" column in that example I would expect the arrow to switch between asc/desc depending on the used order, rather than sticking to asc.