How to turn off sorting with jQueryUI sortable?

I have implemented jQueryUI sortable list and it works really nice. At some point in time, I wish to disable further sorting and keep item order as it is, without user being able to change it.

It tried something this:

$('.sortable').sortable('disable'); 

and this:

$('.sortable').each(function() { $(this).sortable('disable'); });

and:

$('.sortable').disable(); 

and:

$('.sortable').cancel(); 

and various combinations of all that. All without success.

Can anyone tell ne The Right Way™ to do it?

Update: I'm using jQuery 1.3.2 and jQueryUI 1.7.2. A possible problem could be that I have two independent sortable lists on the page, so I have sortable1 and sortable2 classes. I'm actually doing:

$('.sortable2').sortable('disable'); 

Update2: the problem was me using .sortable instead of #sortable. Everything works fine now.