diff --git a/ds.module b/ds.module
index 0e3bc52..52236b6 100644
--- a/ds.module
+++ b/ds.module
@@ -570,14 +570,14 @@ function ds_preprocess_ds_layout(&$variables) {
       $entity_classes = !empty($variables['content']['#ds_configuration']['layout']['entity_classes']) ? $variables['content']['#ds_configuration']['layout']['entity_classes'] : 'old_view_mode';
       if ($entity_classes != 'no_classes') {
         if ($entity_classes == 'all_classes') {
-          $variables['attributes']['class'][] = Html::cleanCssIdentifier($entity_type_id);
-          $variables['attributes']['class'][] = Html::cleanCssIdentifier($entity_type_id) . '--type-' . Html::cleanCssIdentifier($bundle);
-          $variables['attributes']['class'][] = Html::cleanCssIdentifier($entity_type_id) . '--view-mode-' . Html::cleanCssIdentifier($variables['content']['#view_mode']);
+          $variables['attributes']['class'] = array(Html::cleanCssIdentifier($entity_type_id));
+          $variables['attributes']['class'] = array(Html::cleanCssIdentifier($entity_type_id) . '--type-' . Html::cleanCssIdentifier($bundle));
+          $variables['attributes']['class'] = array(Html::cleanCssIdentifier($entity_type_id) . '--view-mode-' . Html::cleanCssIdentifier($variables['content']['#view_mode']));
         }
         elseif ($entity_classes == 'old_view_mode') {
           // Add (old style, non cleaned) view-mode-{name} to classes.
           if (!in_array('view-mode-' . $variables['content']['#view_mode'], $variables['attributes']['class'])) {
-            $variables['attributes']['class'][] = 'view-mode-' . $variables['content']['#view_mode'];
+            $variables['attributes']['class'] = array('view-mode-' . $variables['content']['#view_mode']);
           }
         }
       }