diff --git a/core/config/schema/core.data_types.schema.yml b/core/config/schema/core.data_types.schema.yml
index 3cb2f8c..d75df89 100644
--- a/core/config/schema/core.data_types.schema.yml
+++ b/core/config/schema/core.data_types.schema.yml
@@ -21,7 +21,7 @@ uri:
 # Undefined type to use for missing schema, don't use explicitly.
 undefined:
   label: 'Undefined'
-  class: '\Drupal\Core\Config\Schema\Property'
+  class: '\Drupal\Core\Config\Schema\Undefined'
 
 # Explicit type when no data typing is possible. Avoid if at all possible.
 ignore:
diff --git a/core/lib/Drupal/Core/Config/Schema/Undefined.php b/core/lib/Drupal/Core/Config/Schema/Undefined.php
index d7e4b60..6e98a1a 100644
--- a/core/lib/Drupal/Core/Config/Schema/Undefined.php
+++ b/core/lib/Drupal/Core/Config/Schema/Undefined.php
@@ -2,21 +2,13 @@
 
 /**
  * @file
- * Contains \Drupal\Core\Config\Schema\Sequence.
+ * Contains \Drupal\Core\Config\Schema\Undefined.
  */
 
 namespace Drupal\Core\Config\Schema;
 
 /**
- * Generic configuration property.
+ * Undefined configuration element.
  */
-class Property extends Element {
-
-  /**
-   * Implements TypedDataInterface::validate().
-   */
-  public function validate() {
-    return isset($this->value);
-  }
-
+class Undefined extends Element {
 }
diff --git a/core/lib/Drupal/Core/Config/StorableConfigBase.php b/core/lib/Drupal/Core/Config/StorableConfigBase.php
index c399857..e5b313d 100644
--- a/core/lib/Drupal/Core/Config/StorableConfigBase.php
+++ b/core/lib/Drupal/Core/Config/StorableConfigBase.php
@@ -13,7 +13,7 @@
 use Drupal\Core\TypedData\PrimitiveInterface;
 use Drupal\Core\TypedData\Type\FloatInterface;
 use Drupal\Core\TypedData\Type\IntegerInterface;
-use Drupal\Core\Config\Schema\Property;
+use Drupal\Core\Config\Schema\Undefined;
 
 /**
  * Provides a base class for configuration objects with storage support.
@@ -178,7 +178,7 @@ protected function castValue($key, $value) {
       // Fix as part of https://drupal.org/node/2183983.
     }
     // Do not cast value if it is unknown or defined to be ignored.
-    if ($element && ($element instanceof Property || $element instanceof Ignore)) {
+    if ($element && ($element instanceof Undefined || $element instanceof Ignore)) {
       return $value;
     }
     if ((is_scalar($value) || $value === NULL)) {
diff --git a/core/lib/Drupal/Core/Config/TypedConfigManager.php b/core/lib/Drupal/Core/Config/TypedConfigManager.php
index 647d00f..f587c6e 100644
--- a/core/lib/Drupal/Core/Config/TypedConfigManager.php
+++ b/core/lib/Drupal/Core/Config/TypedConfigManager.php
@@ -326,10 +326,9 @@ protected function replaceVariable($value, $data) {
    * {@inheritdoc}
    */
   public function hasConfigSchema($name) {
-    // The schema system falls back on the Property class for unknown types.
-    // See http://drupal.org/node/1905230
+    // The schema system falls back on the Undefined class for unknown types.
     $definition = $this->getDefinition($name);
-    return is_array($definition) && ($definition['class'] != '\Drupal\Core\Config\Schema\Property');
+    return is_array($definition) && ($definition['class'] != '\Drupal\Core\Config\Schema\Undefined');
   }
 
 }
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigSchemaTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigSchemaTest.php
index 71cdadf..8b129bc 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigSchemaTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigSchemaTest.php
@@ -45,7 +45,7 @@ function testSchemaMapping() {
     $definition = \Drupal::service('config.typed')->getDefinition('config_schema_test.no_such_key');
     $expected = array();
     $expected['label'] = 'Unknown';
-    $expected['class'] = '\Drupal\Core\Config\Schema\Property';
+    $expected['class'] = '\Drupal\Core\Config\Schema\Undefined';
     $this->assertEqual($definition, $expected, 'Retrieved the right metadata for nonexistent configuration.');
 
     // Configuration file without schema will return Unknown as well.
@@ -68,13 +68,13 @@ function testSchemaMapping() {
     $definition = $config['testitem']->getDataDefinition();
     $expected = array();
     $expected['label'] = 'Test item';
-    $expected['class'] = '\Drupal\Core\Config\Schema\Property';
+    $expected['class'] = '\Drupal\Core\Config\Schema\Undefined';
     $expected['type'] = 'undefined';
     $this->assertEqual($definition, $expected, 'Automatic type detected for a scalar is undefined.');
     $definition = $config['testlist']->getDataDefinition();
     $expected = array();
     $expected['label'] = 'Test list';
-    $expected['class'] = '\Drupal\Core\Config\Schema\Property';
+    $expected['class'] = '\Drupal\Core\Config\Schema\Undefined';
     $expected['type'] = 'undefined';
     $this->assertEqual($definition, $expected, 'Automatic type detected for a list is undefined.');
 
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigSchemaTestBase.php b/core/modules/config/lib/Drupal/config/Tests/ConfigSchemaTestBase.php
index a1a43e2..02e7027 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigSchemaTestBase.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigSchemaTestBase.php
@@ -7,7 +7,6 @@
 
 namespace Drupal\config\Tests;
 
-use Drupal\Core\Config\Schema\Property;
 use Drupal\Core\Config\TypedConfigManagerInterface;
 use Drupal\Core\TypedData\Type\BooleanInterface;
 use Drupal\Core\TypedData\Type\StringInterface;