diff --git a/lib/sidekiq/statistic/web_api_extension.rb b/lib/sidekiq/statistic/web_api_extension.rb
index c3be1d8..81d09c9 100644
--- a/lib/sidekiq/statistic/web_api_extension.rb
+++ b/lib/sidekiq/statistic/web_api_extension.rb
@@ -7,7 +7,7 @@ def self.registered(app)
         app.helpers WebExtensionHelper
 
         app.before '/api/*' do
-          content_type :json
+          type = :json
         end
 
         app.get '/api/statistic.json' do