diff --git a/core/lib/Drupal/Core/Config/Schema/Undefined.php b/core/lib/Drupal/Core/Config/Schema/Undefined.php
index 1bcf744..5aa2845 100644
--- a/core/lib/Drupal/Core/Config/Schema/Undefined.php
+++ b/core/lib/Drupal/Core/Config/Schema/Undefined.php
@@ -6,6 +6,8 @@
  */
 
 namespace Drupal\Core\Config\Schema;
+use Drupal\Component\Utility\String;
+use Drupal\Core\Config\ConfigException;
 
 /**
  * Undefined configuration element.
@@ -13,6 +15,15 @@
 class Undefined extends Element {
 
   /**
+   * {@inheritdoc}
+   */
+  protected function parseElement($key, $data, $definition) {
+    // Throw exceptions for undefined elements for testing.
+    throw new ConfigException(String::format("The configuration property @key.@element doesn't exist.", array('@key' => $this->getFullName(), '@element' => $key)));
+    return \Drupal::service('config.typed')->create($definition, $data, $key, $this);
+  }
+
+  /**
    * {@inheritdoc}.
    */
   public function validate() {
diff --git a/core/lib/Drupal/Core/Config/TypedConfigManager.php b/core/lib/Drupal/Core/Config/TypedConfigManager.php
index ba3f353..19811d3 100644
--- a/core/lib/Drupal/Core/Config/TypedConfigManager.php
+++ b/core/lib/Drupal/Core/Config/TypedConfigManager.php
@@ -80,7 +80,7 @@ public function get($name) {
     $data = $this->configStorage->read($name);
     $type_definition = $this->getDefinition($name);
     $data_definition =  $this->buildDataDefinition($type_definition, $data);
-    return $this->create($data_definition, $data);
+    return $this->create($data_definition, $data, $name);
   }
 
   /**