diff --git a/actionpack/lib/abstract_controller/base.rb b/actionpack/lib/abstract_controller/base.rb
index 43cea3b79e577c0cf01bfee4177cceb3791b15bf..b068846a130856a01cb242f1960ac4da00b1ec1b 100644
--- a/actionpack/lib/abstract_controller/base.rb
+++ b/actionpack/lib/abstract_controller/base.rb
@@ -1,4 +1,5 @@
 require 'erubis'
+require 'set'
 require 'active_support/configurable'
 require 'active_support/descendants_tracker'
 require 'active_support/core_ext/module/anonymous'
@@ -59,7 +60,7 @@ def hidden_actions
       # itself. Finally, #hidden_actions are removed.
       #
       # ==== Returns
-      # * <tt>array</tt> - A list of all methods that should be considered actions.
+      # * <tt>set</tt> - A set of all methods that should be considered actions.
       def action_methods
         @action_methods ||= begin
           # All public instance methods of this class, including ancestors
@@ -72,7 +73,7 @@ def action_methods
             hidden_actions.to_a
 
           # Clear out AS callback method pollution
-          methods.reject { |method| method =~ /_one_time_conditions/ }
+          Set.new(methods.reject { |method| method =~ /_one_time_conditions/ })
         end
       end
 
diff --git a/actionpack/test/abstract/abstract_controller_test.rb b/actionpack/test/abstract/abstract_controller_test.rb
index bf068aedcd9a8f8f823e246446e5b2609f9af967..a59a9a3767d71500e13f217fb098cde3b72d8617 100644
--- a/actionpack/test/abstract/abstract_controller_test.rb
+++ b/actionpack/test/abstract/abstract_controller_test.rb
@@ -254,7 +254,7 @@ def index
     class TestActionMethodsReloading < ActiveSupport::TestCase
 
       test "action_methods should be reloaded after defining a new method" do
-        assert_equal ["index"], Me6.action_methods
+        assert_equal Set.new(["index"]), Me6.action_methods
       end
     end