diff -u b/core/modules/config/lib/Drupal/config/Form/ConfigAdminImportForm.php b/core/modules/config/lib/Drupal/config/Form/ConfigAdminImportForm.php
--- b/core/modules/config/lib/Drupal/config/Form/ConfigAdminImportForm.php
+++ b/core/modules/config/lib/Drupal/config/Form/ConfigAdminImportForm.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\config\Form;
 
+use Drupal\Core\ControllerInterface;
 use Drupal\Core\Form\FormInterface;
 use Drupal\Core\Config\StorageInterface;
 use Drupal\Core\Lock;
@@ -15,7 +16,7 @@
 /**
  * Provides a configuration import form.
  */
-class ConfigAdminImportForm implements FormInterface {
+class ConfigAdminImportForm implements FormInterface, ControllerInterface {
 
   /**
    * Stores the source storage to retrieve differences from.
@@ -65,9 +66,6 @@
    * Implements \Drupal\Core\Form\FormInterface::buildForm().
    */
   public function buildForm(array $form, array &$form_state) {
-    $source_storage = $this->sourceStorage;
-    $target_storage = $this->targetStorage;
-
     $form['actions'] = array(
       '#type' => 'actions',
     );
@@ -76,7 +74,7 @@
       '#value' => t('Import all'),
     );
 
-    $source_list = $source_storage->listAll();
+    $source_list = $this->sourceStorage->listAll();
     if (empty($source_list)) {
       $form['no_changes'] = array(
         '#markup' => t('There is no configuration to import.'),
@@ -85,7 +83,7 @@
       return $form;
     }
 
-    $config_changes = config_sync_get_changes($source_storage, $target_storage);
+    $config_changes = config_sync_get_changes($this->sourceStorage, $this->targetStorage);
     if (empty($config_changes)) {
       $form['no_changes'] = array(
         '#markup' => t('There are no configuration changes.'),
@@ -164,9 +162,8 @@
       // Once a sync completes, we empty the staging directory. This prevents
       // changes from being accidentally overwritten by stray files getting
       // imported later.
-      $source_storage = $this->sourceStorage;
-      foreach ($source_storage->listAll() as $name) {
-        $source_storage->delete($name);
+      foreach ($this->sourceStorage->listAll() as $name) {
+        $this->sourceStorage->delete($name);
       }
 
       drupal_flush_all_caches();