fix

config/application.rb

@@ -3,7 +3,10 @@ require File.expand_path('../boot', __FILE__)
 require 'rails/all'
 
 if defined?(Bundler)
-  Bundler.require(:default, :assets, Rails.env)
+  # If you precompile assets before deploying to production, use this line
+  Bundler.require(*Rails.groups(:assets => %w(development test)))
+  # If you want your assets lazily compiled in production, use this line
+  # Bundler.require(:default, :assets, Rails.env)
 end
 
 module Danbooru
@@ -21,3 +24,4 @@ module Danbooru
     config.action_mailer.perform_deliveries = true
   end
 end
+