diff --git a/core/lib/Drupal/Core/Config/Schema/Sequence.php b/core/lib/Drupal/Core/Config/Schema/Sequence.php
index e5b6a35..f49c9ac 100644
--- a/core/lib/Drupal/Core/Config/Schema/Sequence.php
+++ b/core/lib/Drupal/Core/Config/Schema/Sequence.php
@@ -89,4 +89,17 @@ public function set($index, $item) {
     return $this;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function toArray() {
+    return $this->getElements();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setArray(array $items) {
+    // @todo
+  }
 }
diff --git a/core/lib/Drupal/Core/TypedData/ListInterface.php b/core/lib/Drupal/Core/TypedData/ListInterface.php
index ce59dfb..3555dd9 100644
--- a/core/lib/Drupal/Core/TypedData/ListInterface.php
+++ b/core/lib/Drupal/Core/TypedData/ListInterface.php
@@ -90,4 +90,18 @@ public function set($index, $item);
    */
   public function first();
 
+  /**
+    * Returns the array of list items.
+    *
+    * @return array
+    */
+  public function toArray();
+
+  /**
+  * Sets the array of list items.
+  *
+  * @param array $items
+  * The array of list items to set.
+  */
+  public function setArray(array $items);
 }
diff --git a/core/lib/Drupal/Core/TypedData/Plugin/DataType/ItemList.php b/core/lib/Drupal/Core/TypedData/Plugin/DataType/ItemList.php
index 54f3648..1721bdc 100644
--- a/core/lib/Drupal/Core/TypedData/Plugin/DataType/ItemList.php
+++ b/core/lib/Drupal/Core/TypedData/Plugin/DataType/ItemList.php
@@ -250,4 +250,18 @@ public function __clone() {
       }
     }
   }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function toArray() {
+    return $this->list;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setArray(array $items) {
+    $this->list = $items;
+  }
 }