diff --git a/core/config/schema/core.data_types.schema.yml b/core/config/schema/core.data_types.schema.yml
index 8e14b36..d75df89 100644
--- a/core/config/schema/core.data_types.schema.yml
+++ b/core/config/schema/core.data_types.schema.yml
@@ -18,21 +18,20 @@ uri:
   label: 'Uri'
   class: '\Drupal\Core\TypedData\Plugin\DataType\Uri'
 
-# Basic data types for configuration.
+# 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:
+  label: 'Ignore'
+  class: '\Drupal\Core\Config\Schema\Ignore'
+
+# Container data types with lists with known and uknown keys.
 mapping:
   label: Mapping
   class: '\Drupal\Core\Config\Schema\Mapping'
-sequence:
-  label: Sequence
-  class: '\Drupal\Core\Config\Schema\Sequence'
-
-# Default mapping for unknown types or types not found.
-default:
-  type: undefined
-  label: 'Unknown'
 
 # Simple extended data types:
 
diff --git a/core/lib/Drupal/Core/Config/Schema/Ignore.php b/core/lib/Drupal/Core/Config/Schema/Ignore.php
new file mode 100644
index 0000000..a616306
--- /dev/null
+++ b/core/lib/Drupal/Core/Config/Schema/Ignore.php
@@ -0,0 +1,14 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Config\Schema\Ignore.
+ */
+
+namespace Drupal\Core\Config\Schema;
+
+/**
+ * Configuration property to ignore.
+ */
+class Ignore extends Element {
+}
diff --git a/core/lib/Drupal/Core/Config/Schema/Property.php b/core/lib/Drupal/Core/Config/Schema/Property.php
deleted file mode 100644
index d7e4b60..0000000
--- a/core/lib/Drupal/Core/Config/Schema/Property.php
+++ /dev/null
@@ -1,22 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\Core\Config\Schema\Sequence.
- */
-
-namespace Drupal\Core\Config\Schema;
-
-/**
- * Generic configuration property.
- */
-class Property extends Element {
-
-  /**
-   * Implements TypedDataInterface::validate().
-   */
-  public function validate() {
-    return isset($this->value);
-  }
-
-}
diff --git a/core/lib/Drupal/Core/Config/Schema/Undefined.php b/core/lib/Drupal/Core/Config/Schema/Undefined.php
new file mode 100644
index 0000000..6e98a1a
--- /dev/null
+++ b/core/lib/Drupal/Core/Config/Schema/Undefined.php
@@ -0,0 +1,14 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Config\Schema\Undefined.
+ */
+
+namespace Drupal\Core\Config\Schema;
+
+/**
+ * Undefined configuration element.
+ */
+class Undefined extends Element {
+}
diff --git a/core/lib/Drupal/Core/Config/StorableConfigBase.php b/core/lib/Drupal/Core/Config/StorableConfigBase.php
index 18c0f07..e5b313d 100644
--- a/core/lib/Drupal/Core/Config/StorableConfigBase.php
+++ b/core/lib/Drupal/Core/Config/StorableConfigBase.php
@@ -8,10 +8,12 @@
 namespace Drupal\Core\Config;
 
 use Drupal\Component\Utility\String;
+use Drupal\Core\Config\Schema\Ignore;
 use Drupal\Core\Config\Schema\SchemaIncompleteException;
 use Drupal\Core\TypedData\PrimitiveInterface;
 use Drupal\Core\TypedData\Type\FloatInterface;
 use Drupal\Core\TypedData\Type\IntegerInterface;
+use Drupal\Core\Config\Schema\Undefined;
 
 /**
  * Provides a base class for configuration objects with storage support.
@@ -167,37 +169,34 @@ protected function validateValue($key, $value) {
    *   Exception on unsupported/undefined data type deducted.
    */
   protected function castValue($key, $value) {
-    if ($value === NULL) {
-      $value = NULL;
+    $element = FALSE;
+    try {
+      $element = $this->getSchemaWrapper()->get($key);
     }
-    elseif (is_scalar($value)) {
-      try {
-        $element = $this->getSchemaWrapper()->get($key);
-        if ($element instanceof PrimitiveInterface) {
-          // Special handling for integers and floats since the configuration
-          // system is primarily concerned with saving values from the Form API
-          // we have to special case the meaning of an empty string for numeric
-          // types. In PHP this would be casted to a 0 but for the purposes of
-          // configuration we need to treat this as a NULL.
-          if ($value === '' && ($element instanceof IntegerInterface || $element instanceof FloatInterface)) {
-            $value = NULL;
-          }
-          else {
-            $value = $element->getCastedValue();
-          }
+    catch (SchemaIncompleteException $e) {
+      // @todo throw an exception due to an incomplete schema.
+      // Fix as part of https://drupal.org/node/2183983.
+    }
+    // Do not cast value if it is unknown or defined to be ignored.
+    if ($element && ($element instanceof Undefined || $element instanceof Ignore)) {
+      return $value;
+    }
+    if ((is_scalar($value) || $value === NULL)) {
+      if ($element && $element instanceof PrimitiveInterface) {
+        // Special handling for integers and floats since the configuration
+        // system is primarily concerned with saving values from the Form API
+        // we have to special case the meaning of an empty string for numeric
+        // types. In PHP this would be casted to a 0 but for the purposes of
+        // configuration we need to treat this as a NULL.
+        $empty_value =  $value === '' && ($element instanceof IntegerInterface || $element instanceof FloatInterface);
+
+        if ($value === NULL || $empty_value) {
+          $value = NULL;
         }
         else {
-          // Config only supports primitive data types. If the config schema
-          // does define a type $element will be an instance of
-          // \Drupal\Core\Config\Schema\Property. Convert it to string since it
-          // is the safest possible type.
-          $value = $element->getString();
+          $value = $element->getCastedValue();
         }
       }
-      catch (SchemaIncompleteException $e) {
-        // @todo throw an exception due to an incomplete schema.
-        // Fix as part of https://drupal.org/node/2183983.
-      }
     }
     else {
       // Throw exception on any non-scalar or non-array value.
diff --git a/core/lib/Drupal/Core/Config/TypedConfigManager.php b/core/lib/Drupal/Core/Config/TypedConfigManager.php
index 647d00f..f587c6e 100644
--- a/core/lib/Drupal/Core/Config/TypedConfigManager.php
+++ b/core/lib/Drupal/Core/Config/TypedConfigManager.php
@@ -326,10 +326,9 @@ protected function replaceVariable($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 173955f..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.');
 
@@ -254,7 +254,7 @@ public function testConfigSaveWithSchema() {
       'integer' => '100',
       'null_integer' => '',
       'boolean' => 1,
-      // If the config schema doesn't have a type it should be casted to string.
+      // If the config schema doesn't have a type it shouldn't be casted.
       'no_type' => 1,
       'mapping' => array(
         'string' => 1
@@ -277,7 +277,7 @@ public function testConfigSaveWithSchema() {
       'integer' => 100,
       'null_integer' => NULL,
       'boolean' => TRUE,
-      'no_type' => '1',
+      'no_type' => 1,
       'mapping' => array(
         'string' => '1'
       ),
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigSchemaTestBase.php b/core/modules/config/lib/Drupal/config/Tests/ConfigSchemaTestBase.php
index 61eee7e..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;
@@ -92,40 +91,35 @@ public function assertConfigSchema(TypedConfigManagerInterface $typed_config, $c
    *   Returns mixed value.
    */
   protected function checkValue($key, $value) {
+    $element = FALSE;
+    try {
+      $element = $this->schema->get($key);
+    }
+    catch (SchemaIncompleteException $e) {
+      if (is_scalar($value) || $value === NULL) {
+        $this->fail("{$this->configName}:$key has no schema.");
+      }
+    }
+    // Do not check value if it is defined to be ignored.
+    if ($element && $element instanceof Ignore) {
+      return $value;
+    }
+
     if (is_scalar($value) || $value === NULL) {
-      try {
-        $success = FALSE;
-        $type = gettype($value);
-        $element = $this->schema->get($key);
-        if ($element instanceof PrimitiveInterface) {
-          if ($type == 'integer' && $element instanceof IntegerInterface) {
-            $success = TRUE;
-          }
-          if ($type == 'double' && $element instanceof FloatInterface) {
-            $success = TRUE;
-          }
-          if ($type == 'boolean' && $element instanceof BooleanInterface) {
-            $success = TRUE;
-          }
-          if ($type == 'string' && ($element instanceof StringInterface || $element instanceof Property)) {
-            $success = TRUE;
-          }
+      $success = FALSE;
+      $type = gettype($value);
+      if ($element instanceof PrimitiveInterface) {
+        $success =
+          ($type == 'integer' && $element instanceof IntegerInterface) ||
+          ($type == 'double' && $element instanceof FloatInterface) ||
+          ($type == 'boolean' && $element instanceof BooleanInterface) ||
+          ($type == 'string' && $element instanceof StringInterface) ||
           // Null values are allowed for all types.
-          if ($value === NULL) {
-            $success = TRUE;
-          }
-        }
-        else {
-          // @todo throw an exception due to an incomplete schema. Only possible
-          //   once https://drupal.org/node/1910624 is complete.
-        }
-        $class = get_class($element);
-        if (!$success) {
-          $this->fail("{$this->configName}:$key has the wrong schema. Variable type is $type and schema class is $class.");
-        }
+          ($value === NULL);
       }
-      catch (SchemaIncompleteException $e) {
-        $this->fail("{$this->configName}:$key has no schema.");
+      $class = get_class($element);
+      if (!$success) {
+        $this->fail("{$this->configName}:$key has the wrong schema. Variable type is $type and schema class is $class.");
       }
     }
     else {