diff --git a/core/modules/config/lib/Drupal/config/Form/ConfigSingleImportForm.php b/core/modules/config/lib/Drupal/config/Form/ConfigSingleImportForm.php
index 434745e..d38b676 100644
--- a/core/modules/config/lib/Drupal/config/Form/ConfigSingleImportForm.php
+++ b/core/modules/config/lib/Drupal/config/Form/ConfigSingleImportForm.php
@@ -156,6 +156,15 @@ public function buildForm(array $form, array &$form_state) {
       '#rows' => 24,
       '#required' => TRUE,
     );
+    $form['advanced'] = array(
+      '#type' => 'details',
+      '#title' => $this->t('Advanced'),
+    );
+    $form['advanced']['custom_entity_id'] = array(
+      '#title' => $this->t('Custom Entity ID'),
+      '#type' => 'textfield',
+      '#description' => $this->t('Specify a custom entity ID. This will override the entity ID in the configuration above.'),
+    );
     $form['actions'] = array('#type' => 'actions');
     $form['actions']['submit'] = array(
       '#type' => 'submit',
@@ -181,6 +190,13 @@ public function validateForm(array &$form, array &$form_state) {
     if ($form_state['values']['config_type'] !== 'system.simple') {
       $definition = $this->entityManager->getDefinition($form_state['values']['config_type']);
       $id_key = $definition->getKey('id');
+
+      // If a custom entity ID is specified, override the value in the
+      // configuration data being imported.
+      if (!empty($form_state['values']['custom_entity_id'])) {
+        $data[$id_key] = $form_state['values']['custom_entity_id'];
+      }
+
       $entity_storage = $this->entityManager->getStorageController($form_state['values']['config_type']);
       // If an entity ID was not specified, set an error.
       if (!isset($data[$id_key])) {
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigSingleImportExportTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigSingleImportExportTest.php
index fbd7497..44521ad 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigSingleImportExportTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigSingleImportExportTest.php
@@ -73,6 +73,14 @@ public function testImport() {
     $this->drupalPostForm('admin/config/development/configuration/single/import', $edit, t('Import'));
     $this->assertText(t('An entity with this machine name already exists but the UUID does not match.'));
 
+    // Attempt an import with a mismatched UUID and a custom ID.
+    $edit['custom_entity_id'] = 'custom_id';
+    $this->drupalPostForm('admin/config/development/configuration/single/import', $edit, t('Import'));
+    $this->assertRaw(t('Are you sure you want to create new %name @type?', array('%name' => 'custom_id', '@type' => 'test configuration')));
+    $this->drupalPostForm(NULL, array(), t('Confirm'));
+    $entity = $storage->load('custom_id');
+    $this->assertRaw(t('The @entity_type %label was imported.', array('@entity_type' => 'config_test', '%label' => $entity->label())));
+
     // Perform an import with a unique ID and UUID.
     $import = <<<EOD
 id: second