diff --git a/app/controllers/letter_opener_web/application_controller.rb b/app/controllers/letter_opener_web/application_controller.rb
index 96a79b5..a15267f 100644
--- a/app/controllers/letter_opener_web/application_controller.rb
+++ b/app/controllers/letter_opener_web/application_controller.rb
@@ -2,5 +2,6 @@
 
 module LetterOpenerWeb
   class ApplicationController < ActionController::Base
+    protect_from_forgery with: :exception
   end
 end