iconv() Error when uploading SJIS encoded csv in Laravel-Excel

I am uploading a csv with SJIS encoding and I am having the error

iconv(): Detected an illegal character in input string

when processing it using Excel::load. I'm using Laravel 5.2 by the way. Here's my code:

$reader = Excel::load($data,function($reader) {}, 'SJIS');

What should I do with this one? It's my first time to encounter errors like this.

via Chebli Mohamed