diff --git a/core/lib/Drupal/Core/Theme/ThemeInitialization.php b/core/lib/Drupal/Core/Theme/ThemeInitialization.php
index 95ce5f3..0067ee8 100644
--- a/core/lib/Drupal/Core/Theme/ThemeInitialization.php
+++ b/core/lib/Drupal/Core/Theme/ThemeInitialization.php
@@ -41,6 +41,13 @@ class ThemeInitialization implements ThemeInitializationInterface {
   protected $extensions;
 
   /**
+   * The module handler.
+   *
+   * @var \Drupal\Core\Extension\ModuleHandlerInterface
+   */
+  protected $moduleHandler;
+
+  /**
    * Constructs a new ThemeInitialization object.
    *
    * @param string $root