User blog comment:Rappy 4187/Technical Update: January 11, 2016/@comment-30384903-20160112165533/@comment-126761-20160112183524

We recently made a tweak to Dev Wiki that means you'll want to add 'MediaWiki:' into the import references (e.g. " " -> " "), which should fix it.

Requiring this change to import references wasn't intentional - we're looking into working around it.