XMLRPC removes HTML content

I am using a javascript library to send html content wrapped in a div as a new post. The response I get back is a 200 and this body:

<?xml version="1.0" encoding="UTF-8"?>
<methodResponse>
  <params>
    <param>
      <value>
      <string>30</string>
      </value>
    </param>
  </params>
</methodResponse>

The post gets created with title, but there is no content even though I am sending a page worth of html. I have confirmed that the content field in the database is empty.

If I send plain text it works fine.

Not sure how to track this one down…