diff -u b/core/lib/Drupal/Core/Asset/AssetResolver.php b/core/lib/Drupal/Core/Asset/AssetResolver.php
--- b/core/lib/Drupal/Core/Asset/AssetResolver.php
+++ b/core/lib/Drupal/Core/Asset/AssetResolver.php
@@ -124,12 +124,12 @@
           $options['weight'] += count($css) / 1000;
 
           // Local and external files must keep their name as the associative
-          // key so the same CSS file is not added twice.
+          // key so the same CSS file is not added twice. Depending on the type,
+          // some options may need some processing.
           switch ($options['type']) {
             case 'file':
-              // Local CSS files needs the basename to be saved because its
-              // being used for the stylesheet override and remove
-              // functionalities.
+              // Local CSS files need the basename to be saved because it is
+              // used for overriding and removing stylesheets.
               if (!isset($options['basename'])) {
                 $options['basename'] = drupal_basename($options['data']);
               }