2 files changed, 11 insertions, 2 deletions
diff --git a/activerecord/lib/active_record/associations/association_proxy.rb b/activerecord/lib/active_record/associations/association_proxy.rb
index 009e2ec4c2..91da7dec4d 100644
--- a/activerecord/lib/active_record/associations/association_proxy.rb
+++ b/activerecord/lib/active_record/associations/association_proxy.rb
@@ -34,6 +34,10 @@ module ActiveRecord
       end
 
       protected
+        def dependent?
+          @options[:dependent] || false
+        end
+        
         def quoted_record_ids(records)
           records.map { |record| record.quoted_id }.join(',')
         end
diff --git a/activerecord/lib/active_record/associations/has_one_association.rb b/activerecord/lib/active_record/associations/has_one_association.rb
index 30704b6f7e..e566089013 100644
--- a/activerecord/lib/active_record/associations/has_one_association.rb
+++ b/activerecord/lib/active_record/associations/has_one_association.rb
@@ -10,8 +10,13 @@ module ActiveRecord
       def replace(obj, dont_save = false)
         load_target
         unless @target.nil?
-          @target[@association_class_primary_key_name] = nil
-          @target.save unless @owner.new_record?
+          if dependent? && !dont_save     
+            @target.destroy unless @target.new_record?
+            @owner.clear_association_cache
+          else
+            @target[@association_class_primary_key_name] = nil
+            @target.save unless @owner.new_record?
+          end
         end
 
         if obj.nil?