"bundle exec rake" doesn't honor "without"

On a GitLab installation from source, I'm having problems running binaries such as rake. I've never seen similar problems with my own Ruby or Rails projects:

# bundle config
Set for your local app (/mnt/data/www/gitlab.bitcetera.com/source/gitlab/.bundle/config): "1"

path
Set for your local app (/mnt/data/www/gitlab.bitcetera.com/source/gitlab/.bundle/config): "vendor/bundle"

without
Set for your local app (/mnt/data/www/gitlab.bitcetera.com/source/gitlab/.bundle/config): "development:test:unicorn:mysql:kerberos:metrics"

disable_shared_gems
Set for your local app (/mnt/data/www/gitlab.bitcetera.com/source/gitlab/.bundle/config): "true"

# bundle install --deployment --without development test unicorn mysql kerberos metrics
# bundle config
The Gemfile's dependencies are satisfied

# bundle exec rake --tasks
rake aborted!
LoadError: cannot load such file -- haml_lint/rake_task

Looking at the relevant section of the Gemfile:

group :development, :test do
  [...]
  gem 'haml_lint', '~> 0.21.0', require: false
  [...]
end

Of course the haml_lint gem is missing, after all, it's in the "development" and "test" groups only which I've excluded by "without".

Any idea what's going on here?