diff --git a/core/lib/Drupal/Core/Config/Schema/Element.php b/core/lib/Drupal/Core/Config/Schema/Element.php
index c492d42..9f49100 100644
--- a/core/lib/Drupal/Core/Config/Schema/Element.php
+++ b/core/lib/Drupal/Core/Config/Schema/Element.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Config\Schema;
 
+use Drupal\Core\Config\TypedConfigManagerInterface;
 use Drupal\Core\TypedData\TypedData;
 
 /**
@@ -15,6 +16,20 @@
 abstract class Element extends TypedData {
 
   /**
+   * The typed config manager.
+   *
+   * @var \Drupal\Core\Config\TypedConfigManagerInterface
+   */
+  protected $typedConfig;
+
+  /**
+   * @param \Drupal\Core\Config\TypedConfigManagerInterface $typed_config
+   */
+  public function setTypedConfig(TypedConfigManagerInterface $typed_config) {
+    $this->typedConfig = $typed_config;
+  }
+
+  /**
    * The configuration value.
    *
    * @var mixed
@@ -25,7 +40,7 @@
    * Create typed config object.
    */
   protected function parseElement($key, $data, $definition) {
-    return \Drupal::service('config.typed')->create($definition, $data, $key, $this);
+    return $this->typedConfig->create($definition, $data, $key, $this);
   }
 
   /**
@@ -34,7 +49,14 @@ protected function parseElement($key, $data, $definition) {
    * @return \Drupal\Core\TypedData\DataDefinitionInterface
    */
   protected function buildDataDefinition($definition, $value, $key) {
-    return  \Drupal::service('config.typed')->buildDataDefinition($definition, $value, $key, $this);
+    return $this->typedConfig->buildDataDefinition($definition, $value, $key, $this);
   }
 
+//  protected function getTypedConfig() {
+//    if (!isset($this->typedConfig)) {
+//      return \Drupal::service('config.typed');
+//    }
+//    return $this->typedConfig;
+//  }
+
 }
diff --git a/core/lib/Drupal/Core/Config/TypedConfigManager.php b/core/lib/Drupal/Core/Config/TypedConfigManager.php
index fb1c198..2592ac4 100644
--- a/core/lib/Drupal/Core/Config/TypedConfigManager.php
+++ b/core/lib/Drupal/Core/Config/TypedConfigManager.php
@@ -10,6 +10,7 @@
 use Drupal\Component\Utility\NestedArray;
 use Drupal\Core\Cache\CacheBackendInterface;
 use Drupal\Core\Config\Schema\ConfigSchemaDiscovery;
+use Drupal\Core\Config\Schema\Element;
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\TypedData\TypedDataManager;
 
@@ -295,4 +296,21 @@ public function hasConfigSchema($name) {
     return is_array($definition) && ($definition['class'] != '\Drupal\Core\Config\Schema\Undefined');
   }
 
+  protected function alterDefinitions(&$definitions) {
+    $existing = array_keys($definitions);
+    parent::alterDefinitions($definitions); // TODO: Change the autogenerated stub
+    if ($existing !== array_keys($definitions)) {
+      // Throw an exception.
+    }
+  }
+
+  public function createInstance($data_type, array $configuration = array()) {
+    $instance = parent::createInstance($data_type, $configuration);
+    if ($instance instanceof Element) {
+      $instance->setTypedConfig($this);
+    }
+    return $instance;
+  }
+
+
 }
diff --git a/core/lib/Drupal/Core/EventSubscriber/ConfigImportSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/ConfigImportSubscriber.php
index f17d5bd..8e7b885 100644
--- a/core/lib/Drupal/Core/EventSubscriber/ConfigImportSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/ConfigImportSubscriber.php
@@ -7,15 +7,21 @@
 
 namespace Drupal\Core\EventSubscriber;
 
+use Drupal\Core\Cache\MemoryBackend;
+use Drupal\Core\Cache\NullBackend;
 use Drupal\Core\Config\Config;
 use Drupal\Core\Config\ConfigImporterEvent;
 use Drupal\Core\Config\ConfigImportValidateEventSubscriberBase;
 use Drupal\Core\Config\ConfigNameException;
+use Drupal\Core\Config\Schema\SchemaCheckTrait;
+use Drupal\Core\Config\TypedConfigManager;
+use Drupal\Core\Config\InstallStorage;
 
 /**
  * Config import subscriber for config import events.
  */
 class ConfigImportSubscriber extends ConfigImportValidateEventSubscriberBase {
+  use SchemaCheckTrait;
 
   /**
    * Validates the configuration to be imported.
@@ -26,6 +32,13 @@ class ConfigImportSubscriber extends ConfigImportValidateEventSubscriberBase {
    * @throws \Drupal\Core\Config\ConfigNameException
    */
   public function onConfigImporterValidate(ConfigImporterEvent $event) {
+    $schema_storage = new InstallStorage(InstallStorage::CONFIG_SCHEMA_DIRECTORY);
+    $typed_config = new TypedConfigManager(
+      $event->getConfigImporter()->getStorageComparer()->getSourceStorage(),
+      $schema_storage,
+      new MemoryBackend('ConfigImportSubscriber'),
+      \Drupal::moduleHandler()
+    );
     foreach (array('delete', 'create', 'update') as $op) {
       foreach ($event->getConfigImporter()->getUnprocessedConfiguration($op) as $name) {
         try {
@@ -35,6 +48,26 @@ public function onConfigImporterValidate(ConfigImporterEvent $event) {
           $message = $this->t('The config name @config_name is invalid.', array('@config_name' => $name));
           $event->getConfigImporter()->logError($message);
         }
+        if ($op != 'delete') {
+          $config_data = $event->getConfigImporter()
+                               ->getStorageComparer()
+                               ->getSourceStorage()
+                               ->read($name);
+          $errors = $this->checkConfigSchema($typed_config, $name, $config_data);
+          if ($errors === FALSE) {
+            $event->getConfigImporter()
+                  ->logError($this->t('No schema for !config_name', array('!config_name' => $name)));
+          }
+          elseif (is_array($errors)) {
+            foreach ($errors as $key => $error) {
+              $event->getConfigImporter()
+                    ->logError($this->t('Schema key @key failed with: @error', array(
+                      '@key' => $key,
+                      '@error' => $error
+                    )));
+            }
+          }
+        }
       }
     }
   }
diff --git a/core/lib/Drupal/Core/Plugin/DefaultPluginManager.php b/core/lib/Drupal/Core/Plugin/DefaultPluginManager.php
index 95928e4..4f1efaf 100644
--- a/core/lib/Drupal/Core/Plugin/DefaultPluginManager.php
+++ b/core/lib/Drupal/Core/Plugin/DefaultPluginManager.php
@@ -224,9 +224,7 @@ protected function findDefinitions() {
     foreach ($definitions as $plugin_id => &$definition) {
       $this->processDefinition($definition, $plugin_id);
     }
-    if ($this->alterHook) {
-      $this->moduleHandler->alter($this->alterHook, $definitions);
-    }
+    $this->alterDefinitions($definitions);
     // If this plugin was provided by a module that does not exist, remove the
     // plugin definition.
     foreach ($definitions as $plugin_id => $plugin_definition) {
@@ -242,4 +240,16 @@ protected function findDefinitions() {
     return $definitions;
   }
 
+  /**
+   * Invokes the alter hook if set.
+   *
+   * @param $definitions
+   *   The array of definitions found during discovery.
+   */
+  protected function alterDefinitions(&$definitions) {
+    if ($this->alterHook) {
+      $this->moduleHandler->alter($this->alterHook, $definitions);
+    }
+  }
+
 }