MediaWiki is up, but using "Item:" namespace and some "Special:" pages die with a 500 error. Error log says:

2017-03-24 10:58:01: (mod_fastcgi.c.2702) FastCGI-stderr: PHP Catchable fatal error:  Argument 1 passed to Wikibase\SqlIdGenerator::__construct() must be an instance of Wikimedia\Rdbms\LoadBalancer, instance of LoadBalancer given, called in /data/project/comprende/public_html/extensions/Wikibase/repo/includes/Store/Sql/SqlStore.php on line 298 and defined in /data/project/comprende/public_html/extensions/Wikibase/repo/includes/Store/Sql/SqlIdGenerator.php on line 32

IMHO it's bad that a vanilla installation doesn't work out-of-the-box.

Any ideas how to fix this?