Wiki links in forum posts

When writing forum posts it is possible to use MediawikiWiki-like input format. According to the explanation it should be possible to link to pages within the wiki by using the normal wiki syntax ([[Page Title]]). This works pretty well in that it generates a link to http://www.quantiki.org/wiki/Page_Title, which used to be a valid link, but isn't anymore. Now the links have to be on the format http://www.quantiki.org/wiki/index.php/Page_Title. Is it possible to fix this with a configuration setting -- either by making the URL without index.php a valid URL, or changing the way the forum expands internal links?