Setting default snippet ID through REST API

Hello.  We are leveraging the default snippet attribute “mktoDefaultSnippetId” in the div containing the snippet, it is documented here: http://docs.marketo.com/display/public/DOCS/Email+Template+Syntax .  It works when done manually in the UI of Marketo but emails templates created from the REST API fail and the attribute is just stripped out.  Here is the HTML we are generating:

<div class="mktoSnippet" id="viewAsWebpage" mktoDefaultSnippetId="34" mktoName="View as a webpage link" style="padding: 0px 0px 0px 0px;"></div>

Can someone comment on this?