diff -u b/core/lib/Drupal/Core/Config/Schema/ArrayElement.php b/core/lib/Drupal/Core/Config/Schema/ArrayElement.php
--- b/core/lib/Drupal/Core/Config/Schema/ArrayElement.php
+++ b/core/lib/Drupal/Core/Config/Schema/ArrayElement.php
@@ -116 +116 @@
-}
\ No newline at end of file
+}
diff -u b/core/lib/Drupal/Core/Config/Schema/Element.php b/core/lib/Drupal/Core/Config/Schema/Element.php
--- b/core/lib/Drupal/Core/Config/Schema/Element.php
+++ b/core/lib/Drupal/Core/Config/Schema/Element.php
@@ -7,7 +7,7 @@
 
 namespace Drupal\Core\Config\Schema;
 
-use Drupal\Core\TypedData\Type\TypedData;
+use Drupal\Core\TypedData\TypedData;
 
 /**
  * Defines a generic configuration element.
@@ -46,8 +46,7 @@
    * Create typed config object.
    */
   protected function parseElement($key, $data, $definition) {
-    $context = array('name' => $key, 'parent' => $this);
-    return config_typed()->create($definition, $data, $context);
+    return config_typed()->create($definition, $data, $key, $this);
   }
 
 }
diff -u b/core/lib/Drupal/Core/Config/Schema/Mapping.php b/core/lib/Drupal/Core/Config/Schema/Mapping.php
--- b/core/lib/Drupal/Core/Config/Schema/Mapping.php
+++ b/core/lib/Drupal/Core/Config/Schema/Mapping.php
@@ -125 +125 @@
-}
\ No newline at end of file
+}
diff -u b/core/lib/Drupal/Core/Config/Schema/Parser.php b/core/lib/Drupal/Core/Config/Schema/Parser.php
--- b/core/lib/Drupal/Core/Config/Schema/Parser.php
+++ b/core/lib/Drupal/Core/Config/Schema/Parser.php
@@ -15,7 +15,7 @@
   /**
    * Parse configuration data against schema data.
    */
-  static function parse($data, $definition, $context = array()) {
+  static function parse($data, $definition, $name = NULL, $parent = NULL) {
     // Set default type depending on data and context.
     if (!isset($definition['type'])) {
       if (is_array($data) || !$context) {
@@ -26,7 +26,7 @@
       }
     }
     // Create typed data object.
-    config_typed()->create($definition, $data, $context);
+    config_typed()->create($definition, $data, $name, $parent);
   }
 
   /**
diff -u b/core/lib/Drupal/Core/Config/Schema/Property.php b/core/lib/Drupal/Core/Config/Schema/Property.php
--- b/core/lib/Drupal/Core/Config/Schema/Property.php
+++ b/core/lib/Drupal/Core/Config/Schema/Property.php
@@ -22 +22 @@
-}
\ No newline at end of file
+}
diff -u b/core/lib/Drupal/Core/Config/Schema/Sequence.php b/core/lib/Drupal/Core/Config/Schema/Sequence.php
--- b/core/lib/Drupal/Core/Config/Schema/Sequence.php
+++ b/core/lib/Drupal/Core/Config/Schema/Sequence.php
@@ -18,7 +18,7 @@
    * Overrides ArrayElement::parse()
    */
   protected function parse() {
-    $definition = $this->definition['sequence'][0];
+    $definition = $this->getItemDefinition();
     $elements = array();
     foreach ($this->value as $key => $value) {
       $elements[$key] = $this->parseElement($key, $value, $definition);
@@ -36 +36,8 @@
-}
\ No newline at end of file
+  /**
+   * Implements Drupal\Core\TypedData\ListInterface::getItemDefinition().
+   */
+  public function getItemDefinition() {
+    return $this->definition['sequence'][0];
+  }
+
+}
diff -u b/core/lib/Drupal/Core/Config/TypedConfigManager.php b/core/lib/Drupal/Core/Config/TypedConfigManager.php
--- b/core/lib/Drupal/Core/Config/TypedConfigManager.php
+++ b/core/lib/Drupal/Core/Config/TypedConfigManager.php
@@ -9,7 +9,6 @@
 
 use Drupal\Core\Config\Schema\SchemaDiscovery;
 use Drupal\Core\TypedData\TypedDataManager;
-use Drupal\Core\TypedData\TypedDataFactory;
 
 /**
  * Manages config type plugins.
@@ -32,7 +31,7 @@
   public function __construct($storage) {
     $this->storage = $storage;
     $this->discovery = new SchemaDiscovery($storage);
-    $this->factory = new TypedDataFactory($this->discovery);
+    $this->factory = new TypedConfigElementFactory($this->discovery);
   }
 
   /**
@@ -55,7 +54,7 @@
    *
    * Fills in default type and does variable replacement.
    */
-  public function create(array $definition, $value = NULL, array $context = array()) {
+  public function create(array $definition, $value = NULL, $name = NULL, $parent = NULL) {
     if (!isset($definition['type'])) {
       // Set default type 'str' if possible. If not it will be 'any'.
       if (is_string($value)) {
@@ -68,14 +67,16 @@
     elseif (strpos($definition['type'], ']')) {
       // Replace variable names in definition.
       $replace = is_array($value) ? $value : array();
-      if ($context) {
-        $replace['%parent'] = $context['parent']->getValue();
-        $replace['%key'] = $context['name'];
+      if (isset($parent)) {
+        $replace['%parent'] = $parent->getValue();
+      }
+      if (isset($name)) {
+        $replace['%key'] = $name;
       }
       $definition['type'] = $this->replaceName($definition['type'], $replace);
     }
     // Create typed config object.
-    return parent::create($definition, $value, $context);
+    return parent::create($definition, $value, $name, $parent);
   }
 
   /**
diff -u b/core/modules/contact/config/contact.schema.yml b/core/modules/contact/config/contact.schema.yml
--- b/core/modules/contact/config/contact.schema.yml
+++ b/core/modules/contact/config/contact.schema.yml
@@ -34,2 +34,2 @@
-     "user_default_enabled":
-       type: bool
\ No newline at end of file
+      "user_default_enabled":
+        type: bool
only in patch2:
unchanged:
--- /dev/null
+++ b/core/lib/Drupal/Core/Config/TypedConfigElementFactory.php
@@ -0,0 +1,28 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Config\TypedConfigElementFactory.
+ */
+
+namespace Drupal\Core\Config;
+
+use Drupal\Core\TypedData\TypedDataFactory;
+
+/**
+ * A factory for typed config element objects.
+ *
+ * This factory merges the type definition into the element definition prior to
+ * creating the instance.
+ */
+class TypedConfigElementFactory extends TypedDataFactory {
+
+  /**
+   * Overrides Drupal\Core\TypedData\TypedDataFactory::createInstance().
+   */
+  public function createInstance($plugin_id, array $configuration, $name = NULL, $parent = NULL) {
+    $type_definition = $this->discovery->getDefinition($plugin_id);
+    $configuration += $type_definition;
+    return parent::createInstance($plugin_id, $configuration, $name, $parent);
+  }
+}