Upgrading to Laravel 5.2 invalidates all sessions

Upgrading from Laravel 5.1.17 to 5.2. My config/auth.php originally contained:

'driver' => 'eloquent',
'model'  => 'Project\User',
'table'  => 'users',

New file is the same as the default, except with the updated namespace.

'defaults' => [
    'guard' => 'web',
    'passwords' => 'users',
],
'guards' => [
    'web' => [
        'driver' => 'session',
        'provider' => 'users',
    ],
    'api' => [
        'driver' => 'token',
        'provider' => 'users',
    ],
],
'providers' => [
    'users' => [
        'driver' => 'eloquent',
        'model' => Project\User::class,
    ],
],

My env SESSION_DRIVER is redis. I did not clear anything from Redis.

When I upgrade to Laravel 5.2, my user account gets logged out. If I revert back to the previous commit, the user is logged in again. I'm hesitant to upgrade if it's going to invalidate all of my users' sessions and force them to login again. Is there a way to avoid this?

The only other files that were modified were composer.json, composer.lock, app/Exceptions/Handler.php, and config/app.php; nothing that touched Auth.

via Chebli Mohamed