When mod_gzip_send_vary is "on" and a reqheader is defined, mod_gzip will send a Vary header to apprise web caches that there may be different versions of the file available.
The code which generates Vary headers for reqheader entries uses an uninitialized character array, which interacts badly with a broken implementation of mod_gzip_strncpy. The result is that the Vary header is sometimes...
curl --compressed -v -o/dev/null http://your.domain.tld/some/page
then look for "Content-Encoding: gzip"
Do not use the --head option as HEAD requests will not be compressed.
