Thread:Project:Support desk/ !DOCTYPE html missed ?

I found that when mediawiki upgrade to 1.18

the <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">'

become

<!DOCTYPE html>

I tried to set $wgDocType = '-//W3C//DTD XHTML 1.0 Transitional//EN';

But it do not work at all.

My site still show <!DOCTYPE html> in-font of webpage source code.