Context for Focus is ignored

focus.xhtml

<p:messages/>        

<p:focus context="secondGrid"/>

<h:panelGrid columns="2" style="margin-bottom:10px;">
    <h:outputLabel value="Dummy *"/>
    <p:inputText required="true" label="Dummy"/>
</h:panelGrid>

<h:panelGrid id="secondGrid" columns="2">
    <h:outputLabel for="firstname" value="Firstname *"/>
    <p:inputText id="firstname" required="true" label="Firstname"/>

    <h:outputLabel for="surname" value="Surname *"/>
    <p:inputText id="surname" required="true" label="Surname"/>
</h:panelGrid>

<p:commandButton value="Submit" update="@form" style="margin-top:10px;"/>