Laravel 5.1 contract class does not exist

I'm trying to utilize the Laravel database contract instead of the facade (DB::table) and getting:

ReflectionException

Class Illuminate\Contracts\Database does not exist 

Using the Illuminate\Database\DatabaseManager class works fine, but I would prefer not use a concrete class but rather an abstract class (contract/interface) in addition to dependency injection.

Here's what I've tried.

Controller:

<?php namespace App\Http\Controllers;

use Illuminate\Contracts\Database as DB;

class MyController extends Controller
{

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

}

AppServiceProvider:

public function register()
    {
        $this->app->bind(
            'Illuminate\Contracts\Auth\Registrar',
            'App\Services\Registrar',
            'Illuminate\Contracts\Database'
        );
    }

Any help appreciated!

via Chebli Mohamed