Listbox with ROD, problem setting new Listmodel

<zk xmlns:w="http://www.zkoss.org/2005/zk/client">
	<window id="win" border="none" apply="test.ListboxControl">
		<custom-attributes org.zkoss.zul.listbox.rod="true"/>
		<listbox checkmark="true" multiple="true" id="testListbox" height="400px" width="800px">
			<listhead sizable="true">
				<listheader label="Test"/>
			</listhead>
		</listbox>
		
		<button id="btnNewModel" label="Run Bug (make a scroll to the middle first)"/>
	</window>
</zk>

package test;

import java.util.ArrayList;
import java.util.List;

import org.zkoss.zk.ui.Component;
import org.zkoss.zk.ui.util.GenericForwardComposer;
import org.zkoss.zul.ListModelList;
import org.zkoss.zul.Listbox;
import org.zkoss.zul.Listcell;
import org.zkoss.zul.Listitem;
import org.zkoss.zul.ListitemRenderer;

public class ListboxControl extends GenericForwardComposer {

	private Listbox testListbox;

	/**
	 * 
	 */
	private static final long serialVersionUID = -8768290877229863939L;

	@Override
	public void doAfterCompose(Component comp) throws Exception {
		super.doAfterCompose(comp);

		testListbox.setItemRenderer(new ListitemRenderer() {

			@Override
			public void render(Listitem arg0, Object arg1) throws Exception {
				arg0.setValue(arg1);

				DummyItem di = (DummyItem) arg1;

				Listcell lc = new Listcell();

				lc.setLabel(di.getTest());

				lc.setParent(arg0);
			}
		});

		List<DummyItem> ditems = generateDummyItems("First items", 500);

		ListModelList lstModelList = new ListModelList(ditems);

		testListbox.setModel(lstModelList);

	}

	public void onClick$btnNewModel() {
		List<DummyItem> ditems = generateDummyItems("Second items", 5);

		ListModelList lstModelList = new ListModelList(ditems);

		testListbox.setModel(lstModelList);
	}

	public static List<DummyItem> generateDummyItems(String prefix, int size) {

		List<DummyItem> newList = new ArrayList<DummyItem>();

		for (int i = 0; i < size; i++) {
			newList.add(new DummyItem(prefix + i));
		}
		return newList;
	}

	public static class DummyItem {
		protected String test;

		public DummyItem() {

		}

		public DummyItem(String test) {
			setTest(test);
		}

		public String getTest() {
			return test;
		}

		public void setTest(String test) {
			this.test = test;
		}

	}

}