Wikimedia Bugzilla is closed!

In the SpecialStableVersion::getCacheText() method, the result of
Parser::parse() is passed as the first parameter to Parser::replaceVariables().
 That function expects this parameter to be a string, however in later versions
of MediaWiki it will be a ParserOutput object.  This problem can be resolved
simply - and retaining backwards compatibility - by inserting the following text
at line number 384 (i.e. immediately following the line reading: $text =
$p->parse( $text, $title, $parserOptions );):

			$text = is_object($text) ? $text->mText : $text;