Marshaller ignoring setSuppressXSIType

We're using Castor 0.9.6 and the Marshaller seems to be ignoring the following suppress statements:

Marshaller marshaller = new Marshaller(root);
marshaller.setSuppressXSIType(true);
marshaller.setSuppressNamespaces(true);

For example when we marshall objects using the above marshaller we still get XML that looks like this:

<url xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="java:gs.feed.local.url.Url">
<type>Some web page</type>
</url>

when I would expect it to look like this:

<url>
<type>Some web page</type>
</url>

Any suggestions?