Eruby and charset

At the page :

http://www.yvon-thoraval.com/eruby/index.rhtml

the headers give :

Content-type: text/html; charset=iso-8859-1

i don’t know where this info comes from, because it isn’t in my
httpd.conf file and the file itself (index.rhtml) is of UTF-8 encoding.

Then i wonder how to setup eruby for the Content-type charset ???