FormItem label doesn't show when formItem visible and includeInLayout are set dynamically

In the following example

<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx">
<fx:Script><![CDATA[
[Bindable]
public var show:Boolean;
]]></fx:Script>
<s:HGroup>
<mx:Form>
<mx:FormItem label="test">
<mx:TextInput text="test"/>
</mx:FormItem>
<mx:FormItem label="test">
<mx:TextInput text="test"/>
</mx:FormItem>
<mx:FormItem label="test">
<mx:TextInput text="test"/>
</mx:FormItem>

</mx:Form>
<mx:Form>
<mx:FormItem label="test" visible="

{show}" includeInLayout="{show}

">
<mx:TextInput text="test"/>
</mx:FormItem>
<mx:FormItem label="test" visible="

{show}" includeInLayout="{show}

">
<mx:TextInput text="test"/>
</mx:FormItem>
<mx:FormItem label="test" visible="

{show}" includeInLayout="{show}

">
<mx:TextInput text="test"/>
</mx:FormItem>

</mx:Form>
</s:HGroup>
<mx:Button click="show=!show" label="click me" bottom="5" right="5"/>
</s:Application>

Once you press the button, only the textInputs are shown in the second form.