Respond with status code 401 on authentication failure using Laravel and Passport?

I'm configuring a Laravel project to use Passport token authentication. Everything seems to be working, but when the auth:api middleware fails, it responds to the client with a status of 200 and a bunch of HTML in the response body. Instead, I want it to respond with a status of 401.

I can't find anything in the Laravel Passport source or documentation about doing something like this. I can't even find the source for the middleware.

My test route:

Route::get('/protected', function () {
    return response()->json([
        'success' => true
    ]);
})->middleware('auth:api');

config/auth.php

'guards' => [
    'web' => [
        'driver' => 'session',
        'provider' => 'users',
    ],

    'api' => [
        'driver' => 'passport',
        'provider' => 'appUsers',
    ],
],

'providers' => [
    'users' => [
        'driver' => 'eloquent',
        'model' => App\Models\User::class,
    ],

    'appUsers' => [
        'driver' => 'eloquent',
        'model' => App\Models\AppUser::class
    ],
],

via SimpleJ