Composite component woes

[fusiongyro]

This looked like a reasonable way to implement a login/logout link:

  <shiro:guest>
    Welcome, guest! <h:link outcome="pretty:login" value="Login"/>
  </shiro:guest>
  <shiro:authenticated>
    Welcome back, <shiro:principal/>! 
    <h:commandLink value="Logout" action="#{authenticationUI.logout}"/>
  </shiro:authenticated>

This works perfectly in an ordinary Facelets page. But if I move it into a composite component, it works fine except the <shiro:principal/> tag displays the empty string.

Thanks!