Jquery corners on li removes corners

Question

When i click on a li it changes the class to current, which it all works perfectly, but the corners get removed.

Any ideas?

$(document).ready(function() {


    //---- Promo Tabs ----- //

    var
    $tabs = $('.promo-tabs a'),
    $panes = $('.promo-panes > div');

    $tabs.click(function(){
      $(this).addClass('current')
      $(this).parent().siblings().find('a').removeClass('current');
      $panes.eq($tabs.index(this)).fadeIn().siblings().hide();
      return false;
      $btns.first().click();
    });

    //Init Promo Tabs
    $tabs.first().click();


    //---- Slide Tabs ----- //

    var $btns = $('.btns a'), $slides = $('.slides > div');

    $btns.click(function(){
      $(this).addClass('current')
      $(this).parent().siblings().find('a').removeClass('current');
      $slides.eq($btns.index(this)).show('slow').siblings().hide('slow');
      return false;
    });
    $btns.first().click();

    //corners
    $(".promo-tabs li").corner("7px");
    $(".slides").corner("7px");

});