Animation Not Working

Animation Not Working

Hi, I'm having some issues getting a background position to animate. The original position of the image is at 0px -56px, and I'm trying to animate it to come down to 0px 0px.

Here is my code:

   $('#headmenin > a:not(a.sc_up)').bind('mouseenter', function(e){
      $(this).animate({backgroundPosition: '0px 0px'}, 1500 );
   });


It works, but doesn't animate. It just pops in there instantly, not even in the animation time.

Every animation post i see with background-position says to put the 0px 0px in like this '(0px 0px)', but every time I do that, it doesn't work at all.

Any help with this would be appreciated. Thanks!