3 files changed, 22 insertions, 2 deletions
diff --git a/activemodel/CHANGELOG.md b/activemodel/CHANGELOG.md
index 91b25d5cda..eb21b69163 100644
--- a/activemodel/CHANGELOG.md
+++ b/activemodel/CHANGELOG.md
@@ -1,3 +1,8 @@
+*   Updated the `ActiveModel::Dirty#changed_attributes` method to be indifferent between using
+    symbols and strings as keys.
+
+    *William Myers*
+
 *   Added new API methods `reset_changes` and `changed_applied` to `ActiveModel::Dirty`
     that control changes state. Previsously you needed to update internal
     instance variables, but now API methods are available.
diff --git a/activemodel/lib/active_model/dirty.rb b/activemodel/lib/active_model/dirty.rb
index 98e7d84608..c5f1b3f11a 100644
--- a/activemodel/lib/active_model/dirty.rb
+++ b/activemodel/lib/active_model/dirty.rb
@@ -145,7 +145,7 @@ module ActiveModel
     #   person.name = 'robert'
     #   person.changed_attributes # => {"name" => "bob"}
     def changed_attributes
-      @changed_attributes ||= {}
+      @changed_attributes ||= ActiveSupport::HashWithIndifferentAccess.new
     end
 
     # Handle <tt>*_changed?</tt> for +method_missing+.
diff --git a/activemodel/test/cases/dirty_test.rb b/activemodel/test/cases/dirty_test.rb
index ed34ca8a6e..a90d0b1299 100644
--- a/activemodel/test/cases/dirty_test.rb
+++ b/activemodel/test/cases/dirty_test.rb
@@ -3,11 +3,12 @@ require "cases/helper"
 class DirtyTest < ActiveModel::TestCase
   class DirtyModel
     include ActiveModel::Dirty
-    define_attribute_methods :name, :color
+    define_attribute_methods :name, :color, :size
 
     def initialize
       @name = nil
       @color = nil
+      @size = nil
     end
 
     def name
@@ -28,6 +29,15 @@ class DirtyTest < ActiveModel::TestCase
       @color = val
     end
 
+    def size
+      @size
+    end
+
+    def size=(val)
+      attribute_will_change!(:size) unless val == @size
+      @size = val
+    end
+
     def save
       changes_applied
     end
@@ -124,4 +134,9 @@ class DirtyTest < ActiveModel::TestCase
     assert_equal ["Otto", "Mr. Manfredgensonton"], @model.name_change
     assert_equal @model.name_was, "Otto"
   end
+
+  test "using attribute_will_change! with a symbol" do
+    @model.size = 1
+    assert @model.size_changed?
+  end
 end