outdated

after upgrading to PMG-5.1, my ClamAV installation complains about being outdated. E.g. this is what I get when I manually click the "Update Now" button in the web-frontend: ClamAV update process started at Mon Oct 15 14:55:46 2018 WARNING: Your ClamAV installation is OUTDATED! WARNING: Local...

As the title says, the ClamAV database failed to update as the latest version, 1.0.0, is not installed. I have tried "apt-get update && apt-get dist-upgrade" but there was no update available. I could not find any clear document on how to (and should I) fix it. Every help is appreciated!