Use $this->id in relation

Hello,

I have 3 Models: Account, User, Role

Every user could be in different accounts und can have multiple roles in different accounts, e.g. a player(Role-ID 12) in Account 1 and a coach(Role-ID 13) in Account 2.

class Account extends Model
{
public function players(){
        return $this->belongsToMany('App\User')
           ->whereHas('roles', function ($q) {
                $q->where('role_id', 12)->where('account_id', $this->id);
            });
    }
}

Here is the User-Model:

class User extends Model {
    public function roles()
    {
        return $this->belongsToMany(\App\Role::class);
    }
}

Now I will get all players from an account. This works:

$account = Account::findOrfail(2);
$account->players->count(); // 182

Now I will get all players from an account. This works not:

$account = Account::with('players')->findOrfail(2);
$account->players->count(); // 0

I suspect, that I cannot use $this in the relation if I use eager loading. But how can I get the right role for the user.

Thank you for your help!

Alex