Анимированный Halo Tree в Flex 4

[FlashRabbit]

<?xml version="1.0"?>

<s:Application name="TreeTest"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark"
        xmlns:mx="library://ns.adobe.com/flex/halo">
 	<fx:Script>
 		<![CDATA[
 			import mx.effects.easing.Bounce; 			
 		]]>
 	</fx:Script>
    <mx:Tree id="tree1"
            labelField="@label"
            showRoot="true"           
            width="160"
            horizontalCenter="0" 
            verticalCenter="0" 
            openDuration="3000" 
            openEasingFunction="Bounce.easeOut">
        <mx:XMLListCollection id="MailBox">
            <fx:XMLList>
                <folder label="Mail">
                    <folder label="INBOX"/>
                    <folder label="Personal Folder">
                        <Pfolder label="Business" />
                        <Pfolder label="Demo" />
                        <Pfolder label="Personal" isBranch="true" />
                        <Pfolder label="Saved Mail" />
                    </folder>
                    <folder label="Sent" />
                    <folder label="Trash" />
                </folder>
            </fx:XMLList>
        </mx:XMLListCollection>
    </mx:Tree>
 
</s:Application>

Не происходит анимация открытия/закрытия, почему?