Laravel update broke by composer

I am trying to update from Laravel 5.0.35 to 5.1.0. I updated my composer.json file to reflect this, then ran composer update. During the update, symfony/security-core was removed.

- Removing symfony/security-core (v2.6.13)

However, it was never reinstalled. The update finished with an error:

PHP Fatal error:  Interface 'Symfony\Component\Security\Core\User\UserProviderInterface' not found in .../app/Providers/AuthServiceProvider.php on line 14

which was removed as part of removing that package. I don't see anything in the upgrade guide saying this should be removed or deprecated, or how to get around it. Has anyone else run into this? Or is there an easy fix that I'm not seeing? Admittedly I'm relatively new to composer.

Thanks! -Eric

via Chebli Mohamed