Change style of div in border layout cause error of style

https://sourceforge.net/tracker/?func=detail&aid=3300215&group_id=152762&atid=785191

like code below, set background of div in borderlayout when button pressed,
the height of div will become weird.

<zk>
<borderlayout height="450px">
<north title="North" size="40%" flex="true" maxsize="250" splittable="true" collapsible="true">
<div id="div" style="background:#B8D335">
<label value="25%"
style="color:white;font-size:50px" />
</div>
</north>
</borderlayout>
<button label="change color of north" onClick='div.setStyle("background: red")'/>
</zk>