commit 61a0b53453fb097bda07ba54096a68628ee7205a
Author: Erik Stielstra <info@erikstielstra.nl>
Date:   Mon Sep 1 09:06:53 2014 +0200

    #9

diff --git a/core/modules/system/templates/container.html.twig b/core/modules/system/templates/container.html.twig
index 9ec8497..6fb8159 100644
--- a/core/modules/system/templates/container.html.twig
+++ b/core/modules/system/templates/container.html.twig
@@ -17,8 +17,4 @@
  * @ingroup themeable
  */
 #}
-{% if has_parent %}
-  <div{{ attributes.addClass('form-wrapper') }}>{{ children }}</div>
-{% else %}
-  <div{{ attributes }}>{{ children }}</div>
-{% endif %}
+<div{{ attributes.addClass(has_parent ? 'form-wrapper') }}>{{ children }}</div>