Listbox 's scrollbar position is not currect after invalidate() (zk max only)

<zk>
<!-- <custom-attributes org.zkoss.zul.listbox.rod="false"/> -->
<!-- <custom-attributes org.zkoss.zul.grid.rod="false"/> -->
<zscript><![CDATA[
Object[] o = new Object[300]
]]></zscript>
<button label="invalidate">
<attribute name="onClick">
lb.invalidate();
grid.invalidate();
</attribute>
</button>
<hlayout>
<listbox id="lb" width="100px" height="300px">
<listitem label="item" forEach="${o}" />
</listbox>

<grid id="grid" width="100px" height="300px">
<rows>
<row forEach="${o}">item</row>
</rows>
</grid>

</hlayout>
</zk>