diff --git a/core/modules/taxonomy/lib/Drupal/taxonomy/VocabularyFormController.php b/core/modules/taxonomy/lib/Drupal/taxonomy/VocabularyFormController.php
index 168f012..c6ef82d 100644
--- a/core/modules/taxonomy/lib/Drupal/taxonomy/VocabularyFormController.php
+++ b/core/modules/taxonomy/lib/Drupal/taxonomy/VocabularyFormController.php
@@ -38,6 +38,7 @@ class VocabularyFormController extends EntityFormController {
       '#machine_name' => array(
         'exists' => 'taxonomy_vocabulary_load',
       ),
+      '#disabled' => !$vocabulary->isNew(),
     );
     $form['description'] = array(
       '#type' => 'textfield',