placeholder option problem with sortable elements

The 'placeholder' option doesn't work as it should with sortable object. the placeholder styles do not overwrite the element style.

ex :

$(document).ready(function(){
	$(".news_elements").sortable({
		placeholder: "news_elements_empty", 
		revert: true 
	});
});

css :

.news_elements li {
	background-color: blue;
}

.news_elements_empty {
	background-color: red;
}

html :

<ul class="news_elements">
	<li>test1</li>
	<li>test2</li>
	<li>test3</li>
</ul>

When dragging the li, the empty place to drop it is not red. It's blue. But, if you don't defin a background on the LI, then, you'll see the blue one.

You can also try this with the actual last sortable demo on this page :

http://dev.jquery.com/view/tags/ui/latest/demos/functional/#ui.sortable