Laravel cashier with stripe, error checking subscription status

I get the following error when checking subscription status: if ($user->subscribed('main'))

ErrorException in Builder.php line 2405: Call to undefined method
     Illuminate\Database\Query\Builder::valid() (View: /var/www/html...

I don't get any problems using the $user->onGenericTrial() and $user->onTrial() methods in the same view.

I'm using Laravel 5.2 and Cashier 6.0

via Chebli Mohamed