diff --git a/core/lib/Drupal/Core/Config/Schema/ArrayElement.php b/core/lib/Drupal/Core/Config/Schema/ArrayElement.php
index f7fbb3b..c8b1a06 100644
--- a/core/lib/Drupal/Core/Config/Schema/ArrayElement.php
+++ b/core/lib/Drupal/Core/Config/Schema/ArrayElement.php
@@ -79,7 +79,8 @@ 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;
   }
 
@@ -108,6 +109,16 @@ public function toArray() {
   }
 
   /**
+   * {@inheritdoc}
+   */
+  public function onChange($key) {
+    // Notify the parent of changes.
+    if (isset($this->parent)) {
+      $this->parent->onChange($this->name);
+    }
+  }
+
+  /**
    * Implements ArrayAccess::offsetExists().
    */
   public function offsetExists($offset) {
diff --git a/core/lib/Drupal/Core/Config/Schema/ListElementInterface.php b/core/lib/Drupal/Core/Config/Schema/ListElementInterface.php
index 783596f..b6a384f 100644
--- a/core/lib/Drupal/Core/Config/Schema/ListElementInterface.php
+++ b/core/lib/Drupal/Core/Config/Schema/ListElementInterface.php
@@ -69,12 +69,18 @@ public function set($key, $value);
   /**
    * Returns an array of all property values.
    *
-   * Gets an array of plain property values including all not-computed
-   * properties.
-   *
    * @return array
    *   An array of property values, keyed by property name.
    */
   public function toArray();
 
+  /**
+   * React to changes to a child element.
+   *
+   * Note that this is invoked after any changes have been applied.
+   *
+   * @param $key
+   *   The key of the property which is changed.
+   */
+  public function onChange($key);
 }
diff --git a/core/lib/Drupal/Core/Config/Schema/Mapping.php b/core/lib/Drupal/Core/Config/Schema/Mapping.php
index 501e7db..91623e2 100644
--- a/core/lib/Drupal/Core/Config/Schema/Mapping.php
+++ b/core/lib/Drupal/Core/Config/Schema/Mapping.php
@@ -47,7 +47,7 @@ protected function parse() {
    * {@inheritdoc}
    */
   public function set($key, $value) {
-    parent::__set($key, $value);
+    parent::set($key, $value);
     // We may need to rebuild property definitions.
     unset($this->propertyDefinitions);
 
diff --git a/core/modules/config/src/Tests/ConfigSchemaTest.php b/core/modules/config/src/Tests/ConfigSchemaTest.php
index 7401247..fc4f9ae 100644
--- a/core/modules/config/src/Tests/ConfigSchemaTest.php
+++ b/core/modules/config/src/Tests/ConfigSchemaTest.php
@@ -280,8 +280,8 @@ function testSchemaData() {
     $this->assertTrue(isset($list['front']) && isset($list['403']) && isset($list['404']), 'Got a list with the right properties for site page data.');
     $this->assertEqual($list['front']->getValue(), 'user', 'Got the right value for page.front data from the list.');
 
-    // And test some ComplexDataInterface methods.
-    $properties = $list->getProperties();
+    // And test some ListElementInterface methods.
+    $properties = $list->getElements();
     $this->assertTrue(count($properties) == 3 && $properties['front'] == $list['front'], 'Got the right properties for site page.');
     $values = $list->toArray();
     $this->assertTrue(count($values) == 3 && $values['front'] == 'user', 'Got the right property values for site page.');
diff --git a/core/modules/locale/src/Tests/LocaleConfigTranslationTest.php b/core/modules/locale/src/Tests/LocaleConfigTranslationTest.php
index 94ec34d..5befd1a 100644
--- a/core/modules/locale/src/Tests/LocaleConfigTranslationTest.php
+++ b/core/modules/locale/src/Tests/LocaleConfigTranslationTest.php
@@ -81,7 +81,7 @@ function testConfigTranslation() {
 
     // Get translation and check we've only got the site name.
     $translation = $wrapper->getTranslation($langcode);
-    $properties = $translation->getProperties();
+    $properties = $translation->getElements();
     $this->assertEqual(count($properties), 1, 'Got the right number of properties after translation');
 
     // Check the translated site name is displayed.
diff --git a/core/modules/locale/src/Tests/LocaleImportFunctionalTest.php b/core/modules/locale/src/Tests/LocaleImportFunctionalTest.php
index be3c22a..4e02ffd 100644
--- a/core/modules/locale/src/Tests/LocaleImportFunctionalTest.php
+++ b/core/modules/locale/src/Tests/LocaleImportFunctionalTest.php
@@ -297,7 +297,7 @@ function testConfigPoFile() {
     foreach ($config_strings as $config_key => $config_string) {
       $wrapper = $locale_config->get($config_key);
       $translation = $wrapper->getTranslation($langcode);
-      $properties = $translation->getProperties();
+      $properties = $translation->getElements();
       $this->assertEqual(count($properties), 1, 'Got the right number of properties with strict translation');
       $this->assertEqual($properties[$config_string[2]]->getValue(), $config_string[1]);
     }