diff --git a/core/lib/Drupal/Core/Config/StorageComparer.php b/core/lib/Drupal/Core/Config/StorageComparer.php
index 76521629c25dc1cc67ada14560fa988f9a05ebbe..d77f2e6e455e67f6deeebd3f959e22c222e3b44b 100644
--- a/core/lib/Drupal/Core/Config/StorageComparer.php
+++ b/core/lib/Drupal/Core/Config/StorageComparer.php
@@ -205,9 +205,9 @@ public function getChangelist($op = NULL, $collection = StorageInterface::DEFAUL
    *   The change operation performed. Either delete, create, rename, or update.
    * @param array $changes
    *   Array of changes to add to the changelist.
-   * @param array $sort_order
-   *   Array to sort that can be used to sort the changelist. This array must
-   *   contain all the items that are in the change list.
+   * @param array|null $sort_order
+   *   (optional) Array to sort that can be used to sort the changelist. This
+   *   array must contain all the items that are in the change list.
    */
   protected function addChangeList($collection, $op, array $changes, array $sort_order = NULL) {
     // Only add changes that aren't already listed.
diff --git a/core/lib/Drupal/Core/Config/StorageComparerInterface.php b/core/lib/Drupal/Core/Config/StorageComparerInterface.php
index 7961b4ec0fb21aefce72bde2751cf07135ed78af..09e322bf6edd7a60ec49e7a6f46618d32776d072 100644
--- a/core/lib/Drupal/Core/Config/StorageComparerInterface.php
+++ b/core/lib/Drupal/Core/Config/StorageComparerInterface.php
@@ -65,6 +65,14 @@ public function getEmptyChangelist();
    */
   public function getChangelist($op = NULL, $collection = StorageInterface::DEFAULT_COLLECTION);
 
+  /**
+   * Calculates the differences.
+   *
+   * @return $this
+   *   An object which implements the StorageComparerInterface.
+   */
+  public function createChangelist();
+
   /**
    * Recalculates the differences.
    *