diff --git a/core/lib/Drupal/Core/Config/Config.php b/core/lib/Drupal/Core/Config/Config.php
index 469634a..4e86727 100644
--- a/core/lib/Drupal/Core/Config/Config.php
+++ b/core/lib/Drupal/Core/Config/Config.php
@@ -67,7 +67,7 @@ class Config {
    *
    * @var array
    */
-  protected $data;
+  protected $data = array();
 
   /**
    * The current runtime data.