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
diff --git a/core/modules/config/src/Tests/ConfigSchemaTest.php b/core/modules/config/src/Tests/ConfigSchemaTest.php
index 2bbfee5..53503c2 100644
--- a/core/modules/config/src/Tests/ConfigSchemaTest.php
+++ b/core/modules/config/src/Tests/ConfigSchemaTest.php
@@ -315,13 +315,6 @@ function testSchemaData() {
     $this->assertTrue(!$effect['data']->isEmpty() && $effect['id']->getValue() == 'image_scale', 'Got data for the image scale effect from metadata.');
     $this->assertTrue($effect['data']->get('width') instanceof IntegerInterface, 'Got the right type for the scale effect width.');
     $this->assertEqual($effect['data']->get('width')->getValue(), 480, 'Got the right value for the scale effect width.' );
-
-    // Finally update some object using a configuration wrapper.
-    $new_slogan = 'Site slogan for testing configuration metadata';
-    $wrapper = \Drupal::service('config.typed')->get('system.site');
-    $wrapper->set('slogan', $new_slogan);
-    $site_slogan = $wrapper->get('slogan');
-    $this->assertEqual($site_slogan->getValue(), $new_slogan, 'Successfully updated the contained configuration data');
   }
 
   /**