1 files changed, 1 insertions, 3 deletions
diff --git a/activerecord/lib/active_record/validations/uniqueness.rb b/activerecord/lib/active_record/validations/uniqueness.rb
index 31dbf7a889..5db17155c5 100644
--- a/activerecord/lib/active_record/validations/uniqueness.rb
+++ b/activerecord/lib/active_record/validations/uniqueness.rb
@@ -1,5 +1,3 @@
-require 'active_support/core_ext/array/prepend_and_append'
-
 module ActiveRecord
   module Validations
     class UniquenessValidator < ActiveModel::EachValidator # :nodoc:
@@ -53,7 +51,7 @@ module ActiveRecord
         class_hierarchy = [record.class]
 
         while class_hierarchy.first != @klass
-          class_hierarchy.prepend(class_hierarchy.first.superclass)
+          class_hierarchy.unshift(class_hierarchy.first.superclass)
         end
 
         class_hierarchy.detect { |klass| !klass.abstract_class? }