Listbox with paging mold trigger onAfterRender event twice

<zk>
	<zscript><![CDATA[
		String[] ar = new String[30];
		for(int i = 0; i<ar.length; i++) {
			ar[i] = "item " + (i+1);
		}
		BindingListModelList list = new BindingListModelList(Arrays.asList(ar), true);
	]]></zscript>
	<div id="div_test" hflex="1" vflex="1" apply="org.zkoss.zkplus.databind.AnnotateDataBindingComposer">
		<listbox id="listbox_test" vflex="true" mold="paging" pageSize="25" pagingPosition="top" model="${list}" 
			onAfterRender='System.out.println("onAfterRender$listbox_test");'>
			<listhead>
				<listheader label="text" hflex="1" />
			</listhead>
			<listitem self="@{each='item'}" value="@{item}">
				<listcell label="@{item}" />
			</listitem>
		</listbox>
	</div>
</zk>