sidekiq not showing "INFO: Starting processing" when using capistrano-sidekiq

Gemfile.lock

...
capistrano-sidekiq (0.5.4)
  capistrano
  sidekiq (>= 3.4)
...
sidekiq (4.1.1)
  concurrent-ruby (~> 1.0)
  connection_pool (~> 2.2, >= 2.2.0)
  redis (~> 3.2, >= 3.2.1)
...

sidekiq.rb

Sidekiq.configure_server do |config|
  config.redis = { url: 'redis://localhost:6379/1', namespace: "MyApp_#{Rails.env}" }
end

Sidekiq.configure_client do |config|
  config.redis = { url: 'redis://localhost:6379/1', namespace: "MyApp_#{Rails.env}" }
end

sidekiq.yml

---
:verbose: false
:concurrency: 5
:queues:
  - [queue_xyz, 2]
  - [queue_abc, 3]
  - [queue_123, 4]

development:
  :concurrency: 5
staging:
  :concurrency: 10
production:
  :concurrency: 20

staging.rb

set :sidekiq_env, 'staging'
set :sidekiq_config,    ->  { File.join(shared_path, 'config', 'sidekiq.yml') }
set :sidekiq_pid,       ->  { File.join(shared_path, 'tmp', 'pids', 'sidekiq.pid') }
set :sidekiq_log,       ->  { File.join(shared_path, 'log', 'sidekiq.log') }
set :sidekiq_default_hooks, true
set :sidekiq_role, :web