[jQuery] [Cycle] opts.slideCount Problem

a fast question :
how to use the opts.slideCount ?
function onAfter(curr, next, opts){
var msg = ' ' + ( opts.currSlide + 1) + ' / '
+ (opts.slideCount);
$('#counterMedia').html(msg);
};
seems not working easily :
the result in the #counterMedia is :
2 / undefined
the opts.currentSlide works well
but the opts.slideCount not