2 files changed, 12 insertions, 8 deletions
diff --git a/activerecord/lib/active_record/associations/collection_association.rb b/activerecord/lib/active_record/associations/collection_association.rb
index 525ac65722..902ad8cb64 100644
--- a/activerecord/lib/active_record/associations/collection_association.rb
+++ b/activerecord/lib/active_record/associations/collection_association.rb
@@ -423,9 +423,13 @@ module ActiveRecord
           raise NotImplementedError
         end
 
+        def create_scope
+          scoped.scope_for_create.stringify_keys
+        end
+
         def build_record(attributes, options)
-          record = reflection.build_association
-          record.assign_attributes(scoped.scope_for_create, :without_protection => true)
+          record = reflection.build_association(attributes, options)
+          record.assign_attributes(create_scope.except(*record.changed), :without_protection => true)
           record.assign_attributes(attributes, options)
           record
         end
diff --git a/activerecord/lib/active_record/associations/singular_association.rb b/activerecord/lib/active_record/associations/singular_association.rb
index 877ddf3ee1..44dbe984d4 100644
--- a/activerecord/lib/active_record/associations/singular_association.rb
+++ b/activerecord/lib/active_record/associations/singular_association.rb
@@ -26,18 +26,18 @@ module ActiveRecord
       end
 
       def build(attributes = {}, options = {})
-        record = reflection.build_association
-        record.assign_attributes(
-          scoped.scope_for_create.except(klass.primary_key),
-          :without_protection => true
-        )
-        record.assign_attributes(attributes, options)
+        record = reflection.build_association(attributes, options)
+        record.assign_attributes(create_scope.except(*record.changed), :without_protection => true)
         set_new_record(record)
         record
       end
 
       private
 
+        def create_scope
+          scoped.scope_for_create.stringify_keys.except(klass.primary_key)
+        end
+
         def find_target
           scoped.first.tap { |record| set_inverse_instance(record) }
         end