diff --git a/core/lib/Drupal/Core/Extension/ThemeHandlerInterface.php b/core/lib/Drupal/Core/Extension/ThemeHandlerInterface.php
index 91778e3..d24204d 100644
--- a/core/lib/Drupal/Core/Extension/ThemeHandlerInterface.php
+++ b/core/lib/Drupal/Core/Extension/ThemeHandlerInterface.php
@@ -167,7 +167,13 @@ public function getDefault();
    * @return $this
    *
    * @deprecated in Drupal 8.2.x-dev and will be removed before Drupal 9.0.0.
-   *   Use \Drupal::config('system.theme')->set('default', $theme)->save().
+   * Use
+   * @code
+   *   \Drupal::configFactory()
+   *     ->getEditable('system.theme')
+   *     ->set('default', $theme)
+   *     ->save().
+   * @endcode
    */
   public function setDefault($theme);