reverted:
--- b/core/modules/field/theme/field.css
+++ a/core/modules/field/theme/field.css
@@ -26,9 +26,3 @@
 form .field-add-more-submit {
   margin: .5em 0 0;
 }
-
-/* Fieldset variant */
-fieldset.fieldset-no-border {
-  border: none;
-  padding: 0;
-}
diff -u b/core/modules/field_ui/field_ui.admin.inc b/core/modules/field_ui/field_ui.admin.inc
--- b/core/modules/field_ui/field_ui.admin.inc
+++ b/core/modules/field_ui/field_ui.admin.inc
@@ -495,6 +495,9 @@
  * @ingroup forms
  */
 function field_ui_field_settings_form($form, &$form_state, $instance) {
+  $path = drupal_get_path('module', 'field_ui');
+  $form['#attached']['css'][$path . '/field_ui.admin.css'] = array('every_page' => TRUE);
+
   $bundle = $instance['bundle'];
   $entity_type = $instance['entity_type'];
   $field = field_info_field($instance['field_name']);
only in patch2:
unchanged:
--- a/core/modules/field_ui/field_ui.admin.css
+++ b/core/modules/field_ui/field_ui.admin.css
@@ -66,3 +66,9 @@
 .field-ui-overview .field-formatter-settings-edit-form .formatter-name{
   font-weight: bold;
 }
+
+/* Fieldset variant */
+fieldset.fieldset-no-border {
+  border: none;
+  padding: 0;
+}