Composer workflow: How to update composer.lock when I changed a dependence

The project is set-up via composer.phar install --prefer-source and contains quite some modules which are kept in git.

I manage all these modules and their git repositories in my IDE (PhpStorm) and so might commit some changes to some of the modules in the vendor/ folder - directly to the source git repository.

How can I make sure now, that my co-workers get my recent module version when doing a composer.phar install (composer.lock is in the repo)?

If I make a local composer.phar update it looks like the composer.lock is not updated, because I already have the latest version (as I just made the commit directly in the vendor folder)