Steps:
- a2enmod include deflate
- Options Includes MultiViews  # see included .htaccess
- $ cat /var/www/html/test.shtml 
  <!--#include virtual="head"-->
  index
- $ echo "head" > /var/www/html/head.en.html
- $ curl -H'Accept-encoding: gzip, deflate' http://localhost/test.shtml
  head [uncompressed]
  [gzip-compressed index.shtml content]

In Firefox / Chromium, this results in
Content Encoding Error / ERR_CONTENT_DECODING_FAILED
