render html partial from atom builder

So I have an action that results in atom:

def index   ...   respond_to do |format|     ...     format.atom { render :layout => false}   end end

Then I have a builder template to render the atom, called index.atom.builder.

Inside this builder template, I'd like to render one of my existing html partials, to put in the atom:content element, perfectly normal atom thing to do.

xml.content :type => "text/html" do   xml.text! render(:partial => "my_thing") end

The problem is that the template for my_thing is my_thing.html.erb. And since we're somehow in an xml 'context', the render call doesn't find it, it complains that no template could be found.

If I change it to render(:partial => "my_thing.html.erb"), it works... sort of. Because it turns out THAT partial calls OTHER partials, and all of THOSE partial calls would also need to have ".html.erb" added to them.

This is getting messy. Is there some better way to take care of this that involves sweet-talking Rails instead of fighting with it?