Laravel : Failed calling Illuminate\Database\Eloquent\Collection::jsonSerialize()

i'm using Date Mutators to change date format https://laravel.com/docs/5.4/eloquent#date-mutators

When i wrote this code in model :

protected $dates=['birth_date'];
protected $dateFormat = 'Y-m-d';

this exception is thrown :

Failed calling Illuminate\Pagination\LengthAwarePaginator::jsonSerialize()

How i can resolve this problem ??

via ramzi trabelsi