Using EL in attribute of composite component

Question

My JSF custom component code:

<composite:interface name="translation">
    <composite:attribute name="fieldName"/>
  <composite:attribute name="required" default="true" />
</composite:interface>

<composite:implementation>
    <h:inputText required="#{cc.attrs.required}" requiredMessage="Please enter #{cc.attrs.fieldName} in english"/>
</composite:implementation>

This works fine if I specify the required attribute as follows:

<comp:translation fieldName="myTranslation" required="true" />

But does not work if I give EL in required attribute of my composite component:

<comp:translation fieldName="myTranslation" required="#{param['someButtonId'] != null}" />

Can we give EL in attributes of composite components? If yes, then what I am missing?