3 files changed, 20 insertions, 0 deletions
diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 9abfe2e6fd..6e0f1f31dd 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -269,6 +269,11 @@
 
     *Ari Pollak*
 
+*   Fix AR#dup to nullify the validation errors in the dup'ed object. Previously the original
+    and the dup'ed object shared the same errors.
+
+    * Christian Seiler*
+
 *   Raise `ArgumentError` if list of attributes to change is empty in `update_all`.
 
     *Roman Shatsov*
diff --git a/activerecord/lib/active_record/timestamp.rb b/activerecord/lib/active_record/timestamp.rb
index bf95ccb298..dd08a6f4f5 100644
--- a/activerecord/lib/active_record/timestamp.rb
+++ b/activerecord/lib/active_record/timestamp.rb
@@ -42,6 +42,7 @@ module ActiveRecord
 
     def initialize_dup(other) # :nodoc:
       clear_timestamp_attributes
+      super
     end
 
   private
diff --git a/activerecord/test/cases/dup_test.rb b/activerecord/test/cases/dup_test.rb
index 71b2b16608..4e2adff344 100644
--- a/activerecord/test/cases/dup_test.rb
+++ b/activerecord/test/cases/dup_test.rb
@@ -107,5 +107,19 @@ module ActiveRecord
       assert Topic.after_initialize_called
     end
 
+    def test_dup_validity_is_independent
+      Topic.validates_presence_of :title
+      topic = Topic.new("title" => "Litterature")
+      topic.valid?
+
+      duped = topic.dup
+      duped.title = nil
+      assert duped.invalid?
+
+      topic.title = nil
+      duped.title = 'Mathematics'
+      assert topic.invalid?
+      assert duped.valid?
+    end
   end
 end