Airbrake not catching errors for Sidekiq in Rails app on an environment other than development

I'm using Sidekiq and Airbrake in my Rails application. I would like Airbrake to catch any errors that occur during Sidekiq jobs. As per instructions I found online, I've added the following to sidekiq.rb:

config.error_handlers << Proc.new { |ex,context| Airbrake.notify_or_ignore(ex, parameters: context) }

Airbrake then was able to catch errors when they occurred in my development environment. However, once I deployed to a higher environment, Airbrake stopped being able to catch Sidekiq errors. Is there any reason this would happen? Is there anything else I need to configure inside my app?

I'm using sidekiq gem version ~>3.0.2, airbrake gem version ~>4.0.0, and rails 3.2.18

Here is my full sidekiq.rb:

require 'sidekiq'
require 'sidekiq-status'

redis_connection = "redis://127.0.0.1:6379/0"

Sidekiq.configure_server do |config|
  config.redis = { :url => redis_connection, :namespace => 'sidekiq' }
  config.server_middleware do |chain|
    chain.add Sidekiq::Status::ServerMiddleware, expiration: 30.minutes
  end
  config.client_middleware do |chain|
    chain.add Sidekiq::Status::ClientMiddleware
  end
  config.error_handlers << Proc.new { |ex,context| Airbrake.notify_or_ignore(ex, parameters: context) }
end

Sidekiq.configure_client do |config|
  config.redis = { :url => redis_connection, :namespace => 'sidekiq' }

  config.client_middleware do |chain|
    chain.add Sidekiq::Status::ClientMiddleware
  end
end

And here is my full airbrake.rb:

Airbrake.configure do |config|
  config.user_attributes = [:id, :email]
  config.api_key = '*my_api_key*'
end

It turns out that if your app is also using rubber, then you also have to change your rubber sidekiq initializer (config/rubber/common/initializers/sidekiq) to include the line:

config.error_handlers << Proc.new { |ex,context| Airbrake.notify_or_ignore(ex, parameters: context) }

The rubber sidekiq initializer is used for all non-development environments, whereas the sidekiq.rb file is used for development environment.