diff --git a/activesupport/lib/active_support/testing/setup_and_teardown.rb b/activesupport/lib/active_support/testing/setup_and_teardown.rb
index 21d71eb92a..d934246d4d 100644
--- a/activesupport/lib/active_support/testing/setup_and_teardown.rb
+++ b/activesupport/lib/active_support/testing/setup_and_teardown.rb
@@ -18,9 +18,9 @@ def self.included(base)
             alias_method :run, :run_with_callbacks_and_miniunit
           else
             begin
-              require 'mocha'
+              gem 'mocha'
               alias_method :run, :run_with_callbacks_and_mocha
-            rescue LoadError
+            rescue Gem::LoadError
               alias_method :run, :run_with_callbacks_and_testunit
             end
           end