1 files changed, 11 insertions, 8 deletions
diff --git a/activerecord/lib/active_record/nested_attributes.rb b/activerecord/lib/active_record/nested_attributes.rb
index 12a75f5d16..c0302136ea 100644
--- a/activerecord/lib/active_record/nested_attributes.rb
+++ b/activerecord/lib/active_record/nested_attributes.rb
@@ -296,7 +296,9 @@ module ActiveRecord
         assign_to_or_mark_for_destruction(record, attributes, options[:allow_destroy])
 
       elsif attributes['id']
-        raise_nested_attributes_record_not_found(association_name, attributes['id'])
+        existing_record = self.class.reflect_on_association(association_name).klass.find(attributes['id'])
+        assign_to_or_mark_for_destruction(existing_record, attributes, options[:allow_destroy])
+        self.send(association_name.to_s+'=', existing_record)
 
       elsif !reject_new_record?(association_name, attributes)
         method = "build_#{association_name}"
@@ -366,11 +368,16 @@ module ActiveRecord
           unless reject_new_record?(association_name, attributes)
             association.build(attributes.except(*UNASSIGNABLE_KEYS))
           end
+
+        elsif existing_records.count == 0 #Existing record but not yet associated
+          existing_record = self.class.reflect_on_association(association_name).klass.find(attributes['id'])
+          association.send(:add_record_to_target_with_callbacks, existing_record) unless association.loaded?
+          assign_to_or_mark_for_destruction(existing_record, attributes, options[:allow_destroy])
+
         elsif existing_record = existing_records.detect { |record| record.id.to_s == attributes['id'].to_s }
           association.send(:add_record_to_target_with_callbacks, existing_record) unless association.loaded?
           assign_to_or_mark_for_destruction(existing_record, attributes, options[:allow_destroy])
-        else
-          raise_nested_attributes_record_not_found(association_name, attributes['id'])
+
         end
       end
     end
@@ -390,7 +397,7 @@ module ActiveRecord
       ConnectionAdapters::Column.value_to_boolean(hash['_destroy'])
     end
 
-    # Determines if a new record should be build by checking for
+    # Determines if a new record should be built by checking for
     # has_destroy_flag? or if a <tt>:reject_if</tt> proc exists for this
     # association and evaluates to +true+.
     def reject_new_record?(association_name, attributes)
@@ -406,9 +413,5 @@ module ActiveRecord
       end
     end
 
-    def raise_nested_attributes_record_not_found(association_name, record_id)
-      reflection = self.class.reflect_on_association(association_name)
-      raise RecordNotFound, "Couldn't find #{reflection.klass.name} with ID=#{record_id} for #{self.class.name} with ID=#{id}"
-    end
   end
 end