Strange behavior in Laravel queue job

Please consider the following job:

<?php

namespace App\Jobs;

use Illuminate\Contracts\Bus\SelfHandling;
use Illuminate\Contracts\Queue\ShouldQueue;
use Illuminate\Queue\InteractsWithQueue;
use Illuminate\Queue\SerializesModels;

class ImportUsers extends Job implements SelfHandling, ShouldQueue
{
    use InteractsWithQueue, SerializesModels;

    public function __construct($number)
    {
        $this->number=$number;
    }

    public function handle()
    {
        dd($this->number);
        return;
    }
}

Dispatching this job using a sync queue $this->dispatch(new \App\Jobs\ImportUsers(5)); throw this exception: Undefined property: App\Jobs\ImportUsers::$number. This really seems odd for me. Why the handle method can not access class properties?

via Chebli Mohamed