Oops, typo

config/environments/production.rb

@@ -55,7 +55,7 @@ Rails.application.configure do
   # config.logger = ActiveSupport::TaggedLogging.new(SyslogLogger.new)
 
   # Use a different cache store in production.
-  config.cache_store = :memory_store, size: 128.megabytes
+  config.cache_store = :memory_store, { size: 128.megabytes }
 
   # Enable serving of images, stylesheets, and JavaScripts from an asset server.
   # config.action_controller.asset_host = 'http://assets.example.com'