Piwik down since last upgrade - MySQLi error (7 replies)

Hello,

I upgraded last thursday to the latest version (2.8.0). Since then all the graphs are flat. When looking in the logs, I can see MySQL errors:

PHP Fatal error: Call to undefined method Piwik\Db\Adapter\Mysqli::fetch() in /tank/www/piwik/core/Tracker/Model.php on line 353

How comes?

Thanks

Axel