Thread:Project:Support desk/Fatal error ParserCache.php after upgrade from 1.16 to .1.17/reply (4)

You should always upgrade extensions at the same time as you upgrade MediaWiki.

Go to Extension:FlaggedRevs, click "Download snapshot" and download the right version. Make sure, as always, to make a backup of your install and your database before you upgrading stuff. And it's recommended to create a testwiki/clone of your production site and try it there.