This won't work:

<dtml-in qry_user_roles prefix="outer">
  <dtml-in qry_roles>
      <dtml-if expr="outer_role==role">
        Roles are matching
      </dtml-if>
  </dtml-in>
</dtml-in>

I get an error that says key error - outer_role doesn't exist.
It doesn't matter if I prefix the inner dtml-in as well. (I've read it isn't necessary though)
Why won't the prefix work for me?