jQuery UI Selectable : How to get marching ants style lasso to show up?

Question

I've just started injection some jquery UI goodness into my app and am struggling with a rather minor issue. I have the selectable plugin working but I can seem to get the lasso marquee box thing to show up when dragging to select multiple.

Working Example on jquery UI site: http://jqueryui.com/demos/selectable/#default

My Attempt: http://jsbin.com/amare5/2/edit

The code used is an exact copy of the example of the jquery UI site. What am I missing?