Eager Loading Problem

[hakhsin]

Hi, when I define $with property for Eager Loading, I get this error on artisan scout:import.

ErrorException : mb_strtolower() expects parameter 1 to be string, array given

What should I do? My $with property:

    /**
     * The relationships that should always be loaded.
     *
     * @var array
     */
    protected $with = [
        'creator', 'channel'
    ];