Bandbox onChanging cannot update Bandpopup... I think it is a bug?

<div id="searchDiv" apply="${searchModuleController}">
			<bandbox id="searchBox" onChanging="searchModuleController.onChangingSearchBox()">
			<bandpopup id="searchBoxPopup" height="100px">
				<vbox>					
					<listbox id="popupListBox" width="200px" onSelect="searchBox.value=self.selectedItem.label; searchBox.close();">						
						
					</listbox>
				</vbox>
			</bandpopup>
			</bandbox>
			</div>

import java.util.List;

import org.apache.commons.lang.StringUtils;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Component;
import org.zkoss.zk.ui.Executions;
import org.zkoss.zk.ui.Sessions;
import org.zkoss.zul.Bandbox;
import org.zkoss.zul.Bandpopup;
import org.zkoss.zul.Listbox;
import org.zkoss.zul.Listitem;
import org.zkoss.zul.Vbox;

@Component("searchModuleController")
@Scope("page")
public class SearchModuleController extends CBBaseController {
	private Bandbox searchBox;
	private Listbox popupListBox;
	private Bandpopup searchBoxPopup;
	
	
	public void doAfterCompose(org.zkoss.zk.ui.Component comp) throws Exception {
		super.doAfterCompose(comp);		
	}
	
	public void onChangingSearchBox() {
		String text = searchBox.getText();
		
		searchBox.setOpen(false);
		if(StringUtils.isNotBlank(text)) {
			
			int size = popupListBox.getChildren() == null?0: popupListBox.getChildren().size();
			for (int i = 0; i < size; i++) {
				popupListBox.removeItemAt(0);
			}
			
			text = StringUtils.trim(text);
			for(int i=0; i<5; i++) {
				popupListBox.appendChild(new Listitem(text+i));
			}
			popupListBox.renderAll();
		}
		searchBox.setOpen(true);
	}
}