How to change labels in a ButtonBar - simple test case and screenshot attached

In a Flex Mobile app I would like to have a ButtonBar at the bottom and I need to change the labels of its buttons:

(I don't want to use TabbedViewNavigatorApplication here, because all my logic is in a single View with an ActionBar at its top and ButtonBar at its bottom).

So I have prepared a very simple test case to demonstrate my problem.

Please just create a "blank" Flex mobile project in Flash Builder and put my 2 files (below) into it and you will see my problem - touching the buttons at the bottom doesn't change the label of the very right button).

TestAC.mxml:

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" 
               xmlns:s="library://ns.adobe.com/flex/spark" 
               applicationDPI="160">
    <fx:Script>
        <![CDATA[
            import spark.events.IndexChangeEvent;
            import spark.skins.mobile.TabbedViewNavigatorTabBarSkin;

            private function handleTabs(event:IndexChangeEvent):void {
                trace(_tabBar.selectedIndex);
                _tabs[2].label = String(1 + _tabBar.selectedIndex);
            }
        ]]>
    </fx:Script>
    <fx:Declarations>
        <s:MultiDPIBitmapSource id="CHAT" 
            source160dpi="@Embed('chat.png')"
            source240dpi="@Embed('chat.png')"
            source320dpi="@Embed('chat.png')" />

        <s:ArrayCollection id="_tabs">
            <fx:Object label="One" />
            <fx:Object label="Two" />
            <fx:Object label="Three" icon="{CHAT}" />
        </s:ArrayCollection>
    </fx:Declarations>

    <s:ButtonBar id="_tabBar"
                 requireSelection="true" 
                 width="100%" 
                 bottom="0"
                 skinClass="spark.skins.mobile.TabbedViewNavigatorTabBarSkin"
                 dataProvider="{_tabs}"
                 change="handleTabs(event)">
    </s:ButtonBar>

</s:Application>

chat.png:

Allright, adding _tabs.refresh(); to handleTabs has helped.