Placeholder tag in stripes framework

I'm developing a web application using the stripes framework and I would like to use the 'placeholder' tag within a text box like this:

<s:form beanclass="myproject.action.ContactFormActionBean">
  <table class="form">
    <tr>
     <td>Email:</td>
     <td><s:text name="contact.email" placeholder="Please enter your email"></td>
    </tr>
  </table>
</s:form>

However, when I run the page I get a 500 error (Unexpected error). Looking at the stripes documentation, I see that the placeholder attribute is invalid.

Is there a work around that is available for this or do I need to use another tag library in order for placeholder to work?