User blog comment:DaNASCAT/Update Your CSS and JavaScript To Speed Up Your Wiki/@comment-3508190-20120823033542/@comment-4674838-20120823040748

That's correct,  is only available in MediaWiki 1.19+. I would quote an earlier comment where this was verified, but the quote feature isn't in article comments yet :(

As of this week's update, about 30,000 wikis have been upgraded in total. While it's starting to reach the smaller communities, personal test wikis are going to be pretty much last in line. MediaWiki 1.19 coming soon eventually to a theater near you! =)