Updating the image background do not trigger the complete event

I have a div were I update the background css property dynamically. Doing this works as intended:

$('#board-wizard .modal-header').css('background-image', 'url(http://i.imgur.com/WRvMldt.gif)');
$('.modal-header').imagesLoaded( { background: true }, function() {
   console.log('#container background image loaded');
});

But if you change again the background the console.log does not get executed:

$('#board-wizard .modal-header').css('background-image', 'url(anotherImage)');

Is there a work around?