Don't remove the target if it has already been destroyed

2 files changed, 10 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/associations/has_one_association.rb b/activerecord/lib/active_record/associations/has_one_association.rb
index 7134dc85c8..2f3a6e71f1 100644
--- a/activerecord/lib/active_record/associations/has_one_association.rb
+++ b/activerecord/lib/active_record/associations/has_one_association.rb
@@ -10,7 +10,7 @@ module ActiveRecord
 
         reflection.klass.transaction do
           if target && target != record
-            remove_target!(options[:dependent])
+            remove_target!(options[:dependent]) unless target.destroyed?
           end
 
           if record
diff --git a/activerecord/test/cases/associations/has_one_associations_test.rb b/activerecord/test/cases/associations/has_one_associations_test.rb
index 625515f4f1..c2a82b8c60 100644
--- a/activerecord/test/cases/associations/has_one_associations_test.rb
+++ b/activerecord/test/cases/associations/has_one_associations_test.rb
@@ -95,6 +95,15 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
     assert_nil Account.find(old_account_id).firm_id
   end
 
+  def test_natural_assignment_to_nil_after_destroy
+    firm = companies(:rails_core)
+    old_account_id = firm.account.id
+    firm.account.destroy
+    firm.account = nil
+    assert_nil companies(:rails_core).account
+    assert_raise(ActiveRecord::RecordNotFound) { Account.find(old_account_id) }
+  end
+
   def test_association_change_calls_delete
     companies(:first_firm).deletable_account = Account.new(:credit_limit => 5)
     assert_equal [], Account.destroyed_account_ids[companies(:first_firm).id]