diff --git a/core/lib/Drupal/Core/Config/Schema/ArrayElement.php b/core/lib/Drupal/Core/Config/Schema/ArrayElement.php
index 847135e..1b314ac 100644
--- a/core/lib/Drupal/Core/Config/Schema/ArrayElement.php
+++ b/core/lib/Drupal/Core/Config/Schema/ArrayElement.php
@@ -101,18 +101,6 @@ public function get($name) {
   /**
    * {@inheritdoc}
    */
-  public function set($key, $value) {
-    $this->value[$key] = $value;
-    // Parsed elements must be rebuilt with new values
-    unset($this->elements);
-    // Directly notify ourselves.
-    $this->onChange($key, $value);
-    return $this;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
   public function getElements() {
     if (!isset($this->elements)) {
       $this->elements = $this->parse();
diff --git a/core/lib/Drupal/Core/Config/Schema/TypedConfigInterface.php b/core/lib/Drupal/Core/Config/Schema/TypedConfigInterface.php
index 0847df0..0530560 100644
--- a/core/lib/Drupal/Core/Config/Schema/TypedConfigInterface.php
+++ b/core/lib/Drupal/Core/Config/Schema/TypedConfigInterface.php
@@ -54,18 +54,6 @@ public function getElements();
   public function get($name);
 
   /**
-   * Replaces the item at the specified position in this list.
-   *
-   * @param int|string $key
-   *   Property name or index of the item to replace.
-   * @param mixed $value
-   *   Value to be stored at the specified position.
-   *
-   * @return $this
-   */
-  public function set($key, $value);
-
-  /**
    * Returns an array of all property values.
    *
    * @return array