diff --git a/activerecord/lib/active_record/validations/uniqueness.rb b/activerecord/lib/active_record/validations/uniqueness.rb
index 9e4b588ac2c0f..5a24135f8e49b 100644
--- a/activerecord/lib/active_record/validations/uniqueness.rb
+++ b/activerecord/lib/active_record/validations/uniqueness.rb
@@ -26,7 +26,7 @@ def validate_each(record, attribute, value)
         relation = relation.and(table[finder_class.primary_key.to_sym].not_eq(record.send(:id))) if record.persisted?
 
         Array(options[:scope]).each do |scope_item|
-          scope_value = record.send(scope_item)
+          scope_value = record.read_attribute(scope_item)
           reflection = record.class.reflect_on_association(scope_item)
           if reflection
             scope_value = record.send(reflection.foreign_key)
diff --git a/activerecord/test/cases/validations/uniqueness_validation_test.rb b/activerecord/test/cases/validations/uniqueness_validation_test.rb
index c173ee9a15c99..ea5e055289157 100644
--- a/activerecord/test/cases/validations/uniqueness_validation_test.rb
+++ b/activerecord/test/cases/validations/uniqueness_validation_test.rb
@@ -22,6 +22,14 @@ class Conjurer < IneptWizard
 class Thaumaturgist < IneptWizard
 end
 
+class ReplyTitle; end
+
+class ReplyWithTitleObject < Reply
+  validates_uniqueness_of :content, :scope => :title
+
+  def title; ReplyTitle.new; end
+end
+
 class UniquenessValidationTest < ActiveRecord::TestCase
   fixtures :topics, 'warehouse-things', :developers
 
@@ -104,6 +112,14 @@ def test_validate_uniqueness_with_object_scope
     assert !r2.valid?, "Saving r2 first time"
   end
 
+  def test_validate_uniqueness_with_composed_attribute_scope
+    r1 = ReplyWithTitleObject.create "title" => "r1", "content" => "hello world"
+    assert r1.valid?, "Saving r1"
+
+    r2 = ReplyWithTitleObject.create "title" => "r1", "content" => "hello world"
+    assert !r2.valid?, "Saving r2 first time"
+  end
+
   def test_validate_uniqueness_with_object_arg
     Reply.validates_uniqueness_of(:topic)