$(el).css('overflow','hidden').animate(height/width) fails in Safari

[tm]

The following code fails only in Safari:

<div id="wrap" style="width:200px;height:200px">
	<div  style="width:300px;height:300px;background:#eee"></div>
</div>
<input id="doit" type="button" value="do it" />
<script type="text/javascript">
	$('#wrap').css('overflow','hidden');
	$('#doit').toggle(
		function(){ $('#wrap').css('overflow','visible').animate({height:300,width:300},'fast'); },
		function(){ $('#wrap').css('overflow','hidden').animate({height:200,width:200},'fast'); }
		);
</script>