How to make Wisper properly load all subscribers in the app/subscribers directory structure

Rails.application.reloader.to_prepare do
  # Dev env will re-install subscribers on app reload
  Wisper.clear if Rails.env.development?

  Dir[Rails.root.join("app", "subscribers", "**", "*.rb")].each do |listener|
    relative_path = listener.gsub("#{Rails.root}/app/subscribers/", "")
    klass = relative_path.chomp(".rb").camelize.safe_constantize
    Wisper.subscribe(, async: !Rails.env.test?)

Sharing since the sample provided by the project itself won't work with namespaced subscribers.