[Zope] URL0 returns index_html not index.html

Zope 2.7.4 on Debian DTML method index_html in the root says <dtml-var "_['index.html']"> A link in a page template to tal:attributes="href string:${context/REQUEST/URL0}/source.html where the page is addressed by [path]/ and is actually at [path]/index.html returns [path]/index_html/source.html I can vaguely see why this is happening. My question: is there a straightforward way of making the links (and error reports) return the actual page address? (I think I understand that 'actual' 'page' and 'address' are all metaphors which may be leading me into error... ) Thanks for any help/enlightenment. -- Mark Barratt