Use additional gem in deployment

Hello, does anyone have any idea how to add ruby gems if Gemfile.lock exists?

I’m using an application from an apt package but I want to add my custom gem.

I used to be able to do this with bundle install --no-deployment , but when I do that I always get the message

You are trying to install in deployment mode after changing
your Gemfile. Run bundle install elsewhere and add the
updated Gemfile.lock to version control.

If this is a development machine, remove the / opt / zammad / Gemfile freeze
by running bundle install --no-deployment.

The list of sources changed
The dependencies in your gem file changed

You have added to the Gemfile:

  • mySpecialGem