primefaces attribute required in combination with rendered not working

Question

I would like to use a primefaces outpulabel and an inputtext with the attributes "required" and "rendered".

This combination is working:

<p:outputLabel value="Input" for="input" />
<p:inputText id="input" required="true" value="#{myBean.input}"

If I click on a save but and nothing was entered I get the estimated error message.

But If I add the "rendered" attribute it does not work anymore;

<p:outputLabel value="Input" for="input" rendered="<some option is true>"/>
<p:inputText id="input" required="true" value="#{myBean.input}" rendered="<some option is true>"/>

Those elements are wrapped in tags. I use primefaces in version 3.5

Does anyone have an idea whats wrong here?

Thanks