diff --git a/guides/source/action_mailer_basics.md b/guides/source/action_mailer_basics.md
index 9a5204848b3c3bd83e9860aaa3bf53687eb79048..c9e35dd985223312b0cf4e34a70a7d24c913457d 100644
--- a/guides/source/action_mailer_basics.md
+++ b/guides/source/action_mailer_basics.md
@@ -50,7 +50,7 @@ create    test/mailers/previews/user_mailer_preview.rb
 ```ruby
 # app/mailers/application_mailer.rb
 class ApplicationMailer < ActionMailer::Base
-  default "from@example.com"
+  default from: "from@example.com"
   layout 'mailer'
 end