Shared user tables aren't working: You do not have sufficient permissions

I am following this tutorial on how to do shared user tables with dashboard.mysite.com and site.mysite.com. Dashboard is the site that has the user tables. I got this error when I logged into site:

You do not have sufficient permissions to access this page.

I try to follow the tutorial, but on wp-capabilities.php, there is not this line: $this->cap_key = $wpdb->prefix . 'capabilities'; Is it outdated?