Role "tabpanel" rejected for section container

The following HTML5 fragment produces an error:
         <section class="content" id="panel1" role="tabpanel" aria-hidden="true">

This is the error message:

         Error: Bad value tabpanel for attribute role on element section<http://www.w3.org/html/wg/drafts/html/master/single-page.html#the-section-element>.

However the "tabpanel" role is valid and defined here: https://www.w3.org/TR/wai-aria/roles#tabpanel

Please amend the validator, thank you!

Best regards, Ernest