diff -u b/core/themes/seven/seven.theme b/core/themes/seven/seven.theme
--- b/core/themes/seven/seven.theme
+++ b/core/themes/seven/seven.theme
@@ -199,32 +199,20 @@
 }
 
+
 /**
- * Implements hook_library_alter().
+ * Implements hook_library_info_alter().
  */
-function seven_library_alter(&$definition, $library_name) {
-  switch ($library_name) {
-    case 'core/drupal.vertical-tabs':
-      foreach ($definition['css'] as $key => $css) {
-        if ($css['data'] == 'core/misc/vertical-tabs.css') {
-          $definition['css'][$key]['data'] = 'core/themes/seven/css/components/vertical-tabs.css';
-        }
-      }
-      break;
-
-    case 'core/jquery.ui':
-      foreach ($definition['css'] as $key => $css) {
-        if ($css['data'] == 'core/assets/vendor/jquery.ui/themes/base/theme.css') {
-          $definition['css'][$key]['data'] = 'core/themes/seven/css/components/jquery.ui/theme.css';
-        }
-      }
-      break;
-
-    case 'core/drupal.dialog':
-      foreach ($definition['css'] as $key => $css) {
-        if ($css['data'] == 'core/misc/dialog.theme.css') {
-          $definition['css'][$key]['data'] = 'core/themes/seven/css/components/dialog.theme.css';
-        }
-      }
-      break;
+function seven_library_info_alter(&$libraries) {
+  if (isset($libraries['drupal.vertical-tabs'])) {
+    unset($libraries['drupal.vertical-tabs']['css']['component']['misc/vertical-tabs.css']);
+    $libraries['drupal.vertical-tabs']['dependencies'][] = 'seven/vertical-tabs';
+  }
+  if (isset($libraries['jquery.ui'])) {
+    unset($libraries['jquery.ui']['css']['component']['assets/vendor/jquery.ui/themes/base/theme.css']);
+    $libraries['jquery.ui']['dependencies'][] = 'seven/seven.jquery.ui';
+  }
+  if (isset($libraries['drupal.dialog'])) {
+    unset($libraries['drupal.dialog']['css']['component']['misc/dialog.theme.css']);
+    $libraries['drupal.dialog']['dependencies'][] = 'seven/seven.drupal.dialog';
   }
 }
only in patch2:
unchanged:
--- a/core/themes/seven/seven.libraries.yml
+++ b/core/themes/seven/seven.libraries.yml
@@ -72,3 +72,21 @@ drupal.nav-tabs:
     - core/drupal
     - core/jquery.once
     - core/jquery.intrinsic
+
+vertical-tabs:
+  version: VERSION
+  css:
+    theme:
+      css/components/vertical-tabs.css: {}
+
+seven.jquery.ui:
+  version: VERSION
+  css:
+    theme:
+      css/components/jquery.ui/theme.css: {}
+
+seven.drupal.dialog:
+  version: VERSION
+  css:
+    theme:
+      css/components/dialog.theme.css: {}