fanatic/app/Providers/AppServiceProvider.php

<?php

namespace App\Providers;

use Illuminate\Database\Eloquent\Relations\Relation;
use Illuminate\Support\ServiceProvider;

class AppServiceProvider extends ServiceProvider
{
    /**
     * Register any application services.
     *
     * @return void
     */
    public function register()
    {
        //
    }

    /**
     * Bootstrap any application services.
     *
     * @return void
     */
    public function boot()
    {
        Relation::enforceMorphMap([
			'joined' => 'App\Models\Joined',
			'owned'  => 'App\Models\Owned',
			'wish'   => 'App\Models\Wish',
		]);
    }
}