diff --git a/actionmailer/lib/rails/generators/mailer/templates/mailer.rb b/actionmailer/lib/rails/generators/mailer/templates/mailer.rb
index b9be70a2f0..348d314758 100644
--- a/actionmailer/lib/rails/generators/mailer/templates/mailer.rb
+++ b/actionmailer/lib/rails/generators/mailer/templates/mailer.rb
@@ -5,7 +5,7 @@ class <%= class_name %>Mailer < ApplicationMailer
   # Subject can be set in your I18n file at config/locales/en.yml
   # with the following lookup:
   #
-  #   en.<%= file_path.tr("/",".") %>.<%= action %>.subject
+  #   en.<%= file_path.tr("/",".") %>_mailer.<%= action %>.subject
   #
   def <%= action %>
     @greeting = "Hi"
diff --git a/railties/test/generators/mailer_generator_test.rb b/railties/test/generators/mailer_generator_test.rb
index 8d2d97f64f..febd2fd12e 100644
--- a/railties/test/generators/mailer_generator_test.rb
+++ b/railties/test/generators/mailer_generator_test.rb
@@ -26,8 +26,8 @@ class MailerGeneratorTest < Rails::Generators::TestCase
   def test_mailer_with_i18n_helper
     run_generator
     assert_file "app/mailers/notifier_mailer.rb" do |mailer|
-      assert_match(/en\.notifier\.foo\.subject/, mailer)
-      assert_match(/en\.notifier\.bar\.subject/, mailer)
+      assert_match(/en\.notifier_mailer\.foo\.subject/, mailer)
+      assert_match(/en\.notifier_mailer\.bar\.subject/, mailer)
     end
   end
 
@@ -126,7 +126,7 @@ class MailerGeneratorTest < Rails::Generators::TestCase
     run_generator ["Farm::Animal", "moos"]
     assert_file "app/mailers/farm/animal_mailer.rb" do |mailer|
       assert_match(/class Farm::AnimalMailer < ApplicationMailer/, mailer)
-      assert_match(/en\.farm\.animal\.moos\.subject/, mailer)
+      assert_match(/en\.farm\.animal_mailer\.moos\.subject/, mailer)
     end
     assert_file "test/mailers/previews/farm/animal_mailer_preview.rb" do |preview|
       assert_match(/\# Preview all emails at http:\/\/localhost\:3000\/rails\/mailers\/farm\/animal/, preview)
diff --git a/railties/test/generators/namespaced_generators_test.rb b/railties/test/generators/namespaced_generators_test.rb
index a4dad1f2b4..d0ea01dfb0 100644
--- a/railties/test/generators/namespaced_generators_test.rb
+++ b/railties/test/generators/namespaced_generators_test.rb
@@ -156,8 +156,8 @@ class NamespacedMailerGeneratorTest < NamespacedGeneratorTestCase
   def test_mailer_with_i18n_helper
     run_generator
     assert_file "app/mailers/test_app/notifier_mailer.rb" do |mailer|
-      assert_match(/en\.notifier\.foo\.subject/, mailer)
-      assert_match(/en\.notifier\.bar\.subject/, mailer)
+      assert_match(/en\.notifier_mailer\.foo\.subject/, mailer)
+      assert_match(/en\.notifier_mailer\.bar\.subject/, mailer)
     end
   end