diff --git a/actionmailer/lib/action_mailer/test_case.rb b/actionmailer/lib/action_mailer/test_case.rb
index 4e48c0260f..529140dfad 100644
--- a/actionmailer/lib/action_mailer/test_case.rb
+++ b/actionmailer/lib/action_mailer/test_case.rb
@@ -1,3 +1,4 @@
+require 'active_support/test_case'
 require 'active_support/core_ext/class/attribute'
 
 module ActionMailer
diff --git a/actionmailer/test/asset_host_test.rb b/actionmailer/test/asset_host_test.rb
index b24eca5fbb..696a9f1174 100644
--- a/actionmailer/test/asset_host_test.rb
+++ b/actionmailer/test/asset_host_test.rb
@@ -9,7 +9,7 @@ class AssetHostMailer < ActionMailer::Base
   end
 end
 
-class AssetHostTest < Test::Unit::TestCase
+class AssetHostTest < ActiveSupport::TestCase
   def setup
     set_delivery_method :test
     ActionMailer::Base.perform_deliveries = true
diff --git a/actionmailer/test/mail_layout_test.rb b/actionmailer/test/mail_layout_test.rb
index def8da81b8..71e93c29f1 100644
--- a/actionmailer/test/mail_layout_test.rb
+++ b/actionmailer/test/mail_layout_test.rb
@@ -43,7 +43,7 @@ class ExplicitLayoutMailer < ActionMailer::Base
   end
 end
 
-class LayoutMailerTest < Test::Unit::TestCase
+class LayoutMailerTest < ActiveSupport::TestCase
   def setup
     set_delivery_method :test
     ActionMailer::Base.perform_deliveries = true