django - XML Parsing Error: prefix not bound to a namespace

I get the following error -

XML Parsing Error: prefix not bound to a namespace

When trying to generate XML in django where the key contains a colon. If I remove the : from the key there's no error. Unfortunately the : needs to be there so I need to understand why the XML Parser is failing on the : and how to correct it. I'm assuming I need to create a custom Parser.

Here's a sample of how the XML would look -

<entry>
    <id></id>
    <name></name>
    <source></source>
    <tes:variable>
        <tes:type></tes:type>
    </tes:variable>
</entry>