How to debug Apache Multiviews site

My site uses Apache Multiviews for multi-language support, where the server does an implicit filename pattern match and chooses the best match among the results. Like, if index.html doesn't exist, it checks for index.* and select the best matching one. In my cases this is either index.hmtl.en or index.html.de.

I configured the editor to recognize these patterns. But, how can I tell the internal web server, that it should handle the files as HTML and serve them?