diff --git a/core/core.services.yml b/core/core.services.yml
index 8fe29d2..1608ce0 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -1076,7 +1076,7 @@ services:
     class: Drupal\Core\EventSubscriber\ConfigImportSubscriber
     tags:
       - { name: event_subscriber }
-    arguments: ['@theme_handler']
+    arguments: ['@theme_handler', '@module_installer']
   config_snapshot_subscriber:
     class: Drupal\Core\EventSubscriber\ConfigSnapshotSubscriber
     tags:
diff --git a/core/lib/Drupal/Core/EventSubscriber/ConfigImportSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/ConfigImportSubscriber.php
index 6a69082..cd4d989 100644
--- a/core/lib/Drupal/Core/EventSubscriber/ConfigImportSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/ConfigImportSubscriber.php
@@ -12,6 +12,7 @@
 use Drupal\Core\Config\ConfigImporterEvent;
 use Drupal\Core\Config\ConfigImportValidateEventSubscriberBase;
 use Drupal\Core\Config\ConfigNameException;
+use Drupal\Core\Extension\ModuleInstallerInterface;
 use Drupal\Core\Extension\ThemeHandlerInterface;
 use Drupal\Core\Site\Settings;
 
@@ -42,13 +43,23 @@ class ConfigImportSubscriber extends ConfigImportValidateEventSubscriberBase {
   protected $themeHandler;
 
   /**
+   * The theme handler.
+   *
+   * @var \Drupal\Core\Extension\ThemeHandlerInterface
+   */
+  protected $moduleInstaller;
+
+  /**
    * Constructs the ConfigImportSubscriber.
    *
    * @param \Drupal\Core\Extension\ThemeHandlerInterface $theme_handler
    *   The theme handler.
+   * @param \Drupal\Core\Extension\ModuleInstallerInterface $module_installer
+   *   The module installer.
    */
-  public function __construct(ThemeHandlerInterface $theme_handler) {
+  public function __construct(ThemeHandlerInterface $theme_handler, ModuleInstallerInterface $module_installer) {
     $this->themeHandler = $theme_handler;
+    $this->moduleInstaller = $module_installer;
   }
 
   /**
@@ -133,6 +144,14 @@ protected function validateModules(ConfigImporter $config_importer) {
       }
     }
 
+    // Ensure that modules can be uninstalled.
+    if ($reasons = $this->moduleInstaller->validateUninstall($uninstalls)) {
+      foreach ($reasons as $module => $reason) {
+        $module_name = $module_data[$module]->info['name'];
+        $config_importer->logError($this->t('Unable to uninstall the %module module because: !reason.', array('%module' => $module_name, '!reason' => implode(', ', $reason))));
+      }
+    }
+
     // Ensure that the install profile is not being uninstalled.
     if (in_array($install_profile, $uninstalls)) {
       $profile_name = $module_data[$install_profile]->info['name'];
diff --git a/core/modules/config/src/Tests/ConfigImporterTest.php b/core/modules/config/src/Tests/ConfigImporterTest.php
index e39baf6..89c7a6c 100644
--- a/core/modules/config/src/Tests/ConfigImporterTest.php
+++ b/core/modules/config/src/Tests/ConfigImporterTest.php
@@ -649,6 +649,29 @@ public function testMissingCoreExtension() {
   }
 
   /**
+   * Tests uninstall validators being called during synchronisation.
+   *
+   * @see \Drupal\Core\EventSubscriber\ConfigImportSubscriber
+   */
+  public function testMissingExtensionValidation() {
+    $staging = $this->container->get('config.storage.staging');
+    $extensions = $staging->read('core.extension');
+    // Remove the config_test module.
+    unset($extensions['module']['system']);
+    $staging->write('core.extension', $extensions);
+
+    try {
+      $this->configImporter->reset()->import();
+      $this->fail('ConfigImporterException not thrown, invalid import was not stopped due to missing dependencies.');
+    }
+    catch (ConfigImporterException $e) {
+      $this->assertEqual($e->getMessage(), 'There were errors validating the config synchronization.');
+      $error_log = $this->configImporter->getErrors();
+      $this->assertEqual(['Unable to uninstall the <em class="placeholder">System</em> module because: The System module is required.'], $error_log);
+    }
+  }
+
+  /**
    * Tests install profile validation during configuration import.
    *
    * @see \Drupal\Core\EventSubscriber\ConfigImportSubscriber