diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index 95adc95..92e657f 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -3166,7 +3166,7 @@ function _registry_check_code($type, $name = NULL) {
   $cache_key = $type[0] . $name;
   if (isset($lookup_cache[$cache_key])) {
     if ($lookup_cache[$cache_key]) {
-      require_once DRUPAL_ROOT . '/' . $lookup_cache[$cache_key];
+      include_once DRUPAL_ROOT . '/' . $lookup_cache[$cache_key];
     }
     return (bool) $lookup_cache[$cache_key];
   }
@@ -3188,7 +3188,7 @@ function _registry_check_code($type, $name = NULL) {
   $lookup_cache[$cache_key] = $file;
 
   if ($file) {
-    require_once DRUPAL_ROOT . '/' . $file;
+    include_once DRUPAL_ROOT . '/' . $file;
     return TRUE;
   }
   else {
diff --git a/core/modules/config/config.admin.inc b/core/modules/config/config.admin.inc
index 1fe14b2..87a1463 100644
--- a/core/modules/config/config.admin.inc
+++ b/core/modules/config/config.admin.inc
@@ -60,6 +60,21 @@ function config_admin_import_form($form, &$form_state) {
   $source_storage = new FileStorage();
   $target_storage = new DatabaseStorage();
 
+  // Prevent users from deleting all configuration.
+  // If the source storage is empty, that signals the unique condition of not
+  // having exported anything at all, and thus no valid storage to compare the
+  // active storage against.
+  // @todo StorageInterface::listAll() can easily yield hundreds or even
+  //   thousands of entries; consider to add a dedicated isEmpty() method for
+  //   storage controllers.
+  $all = $source_storage->listAll();
+  if (empty($all)) {
+    form_set_error('', t('There is no base configuration. <a href="@export-url">Export</a> it first.', array(
+      '@export-url' => url('admin/config/development/sync/export'),
+    )));
+    return $form;
+  }
+
   config_admin_sync_form($form, $form_state, $source_storage, $target_storage);
 
   $form['actions'] = array('#type' => 'actions');
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigImportUITest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigImportUITest.php
index 6b64b22..cdd2704 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigImportUITest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigImportUITest.php
@@ -74,8 +74,14 @@ class ConfigImportUITest extends WebTestBase {
     $this->assertIdentical($file_storage->exists($name), FALSE, $name . ' not found.');
     $this->assertIdentical($file_storage->exists($dynamic_name), FALSE, $dynamic_name . ' not found.');
 
-    // Export.
-    config_export();
+    // Verify that the import UI does not allow to import without exported
+    // configuration.
+    $this->drupalGet('admin/config/development/sync');
+    $this->assertText('There is no base configuration.');
+
+    // Verify that the Export link yields to the export UI page, and export.
+    $this->clickLink('Export');
+    $this->drupalPost(NULL, array(), t('Export'));
 
     // Create new configuration objects.
     $file_storage->write($name, array(
@@ -111,6 +117,14 @@ class ConfigImportUITest extends WebTestBase {
    * Tests concurrent importing of configuration.
    */
   function testImportLock() {
+    $name = 'config_test.new';
+
+    // Write a configuration object to import.
+    $file_storage = new FileStorage();
+    $file_storage->write($name, array(
+      'add_me' => 'new value',
+    ));
+
     // Verify that there are configuration differences to import.
     $this->drupalGet('admin/config/development/sync');
     $this->assertNoText(t('There are no configuration changes.'));