After upgrading a website to 4.0 I get the following error: Fatal error: Class 'SiteTree' not found, in Page.php.
Or at least can someone put me on the right path of upgrading this. Couldn't really find a good tutorial or anything that says exactly what to do.
What I actually done was: I downloaded from GitHub the latest silverstripe 4.0 and copyied the files over the site ( excluding themes and mysite).