When developing a Laravel package how to specify version of Laravel?

If I am creating a package, specifically for Laravel, how can I "describe" (in my composer.json) that it only works with Laravel 5.3?

For example, in my package I am using Laravel's Session (illuminate/session) and I use Session::set() which is removed from Laravel in 5.4? I don't want people to upgrade their Laravel projects and break their code, because my package doesn't have a version that supports new Laravel features. I want them to get notified by composer when upgrading, so I think I should specify something additional in my package's composer.json.