We are on .2019 at the moment, this is the download link :

Download locations
http://files.avast.com/beta9x/avast_free_antivirus_setup.exe
http://files.avast.com/beta9x/avast_pro_antivirus_setup.exe
http://files.avast.com/beta9x/avast_internet_security_setup.exe
http://files.avast.com/beta9x/avast_premier_antivirus_setup.exe

An overinstall should work