2 files changed, 17 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/attribute.rb b/activerecord/lib/active_record/attribute.rb
index cacde0f6fd..9530f134d0 100644
--- a/activerecord/lib/active_record/attribute.rb
+++ b/activerecord/lib/active_record/attribute.rb
@@ -205,6 +205,8 @@ module ActiveRecord
     end
 
     class Uninitialized < Attribute # :nodoc:
+      UNINITIALIZED_ORIGINAL_VALUE = Object.new
+
       def initialize(name, type)
         super(name, nil, type)
       end
@@ -215,6 +217,10 @@ module ActiveRecord
         end
       end
 
+      def original_value
+        UNINITIALIZED_ORIGINAL_VALUE
+      end
+
       def value_for_database
       end
 
diff --git a/activerecord/test/cases/dirty_test.rb b/activerecord/test/cases/dirty_test.rb
index a3f8d26100..7ad9ff1f57 100644
--- a/activerecord/test/cases/dirty_test.rb
+++ b/activerecord/test/cases/dirty_test.rb
@@ -734,6 +734,17 @@ class DirtyTest < ActiveRecord::TestCase
     assert_equal "arr", pirate.catchphrase
   end
 
+  test "attributes assigned but not selected are dirty" do
+    person = Person.select(:id).first
+    refute person.changed?
+
+    person.first_name = "Sean"
+    assert person.changed?
+
+    person.first_name = nil
+    assert person.changed?
+  end
+
   private
     def with_partial_writes(klass, on = true)
       old = klass.partial_writes?