Specifying morphTo method target id column

Is there a way to specify target id column on morphTo method?

I'll give an example which is in documentation for laravel:

Post - Id, text

Video - Id, url

Comment - Id, text, commentable_id, commentable_type

But what if Ids on post and video were renamed to custom_id? How would I set up my eloquent model then? Thanks.

Edit:

I still don't get it here is the complete code:

Table structure:

comments - id, text, commentable_id, commentable_type, user_id
posts - custom_id, text
videos - custom_id, url
users - id, name, email, password,...

Comment model:

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Comment extends Model
{
    public function commentable()
    {
        return $this->morphTo();
    }
}

Video model:

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Video extends Model
{

    public function comments()
    {
        return $this->morphMany('App\Comment', 'commentable', 'commentable_type', 'commentable_id', 'custom_id');
    }
}

Post model:

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Post extends Model
{
    public function comments()
    {
        return $this->morphMany('App\Comment', 'commentable', 'commentable_type', 'commentable_id', 'custom_id');
    }
}

User model:

<?php

namespace App;

use Illuminate\Notifications\Notifiable;
use Illuminate\Foundation\Auth\User as Authenticatable;

class User extends Authenticatable
{
    use Notifiable;

    /**
     * The attributes that are mass assignable.
     *
     * @var array
     */
    protected $fillable = [
        'name', 'email', 'password',
    ];

    /**
     * The attributes that should be hidden for arrays.
     *
     * @var array
     */
    protected $hidden = [
        'password', 'remember_token',
    ];

    public function comments()
    {
        return $this->hasMany('App\Comment');
    }
}

TestController:

<?php

namespace App\Http\Controllers;

use App\User;
use Illuminate\Http\Request;

class TestController extends Controller
{
    public function test()
    {
        $user = User::first();
        $comments = $user -> comments;

        foreach ($comments as $comment)
        {
            return $comment -> commentable;
        }
    }
}

And it still throws query exception Unknown column posts.id

Please explain. Thanks.

via M. Novotny