diff --git a/core/modules/taxonomy/taxonomy.module b/core/modules/taxonomy/taxonomy.module
index 0f8b6b5..3a7fc51 100644
--- a/core/modules/taxonomy/taxonomy.module
+++ b/core/modules/taxonomy/taxonomy.module
@@ -70,13 +70,15 @@ function taxonomy_help($path, $arg) {
       return $output;
     case 'admin/structure/taxonomy/%':
       $vocabulary = taxonomy_vocabulary_machine_name_load($arg[3]);
-      switch ($vocabulary->hierarchy) {
+      if ($vocabulary) {
+        switch ($vocabulary->hierarchy) {
         case TAXONOMY_HIERARCHY_DISABLED:
           return '<p>' . t('You can reorganize the terms in %capital_name using their drag-and-drop handles, and group terms under a parent term by sliding them under and to the right of the parent.', array('%capital_name' => drupal_ucfirst($vocabulary->name), '%name' => $vocabulary->name)) . '</p>';
         case TAXONOMY_HIERARCHY_SINGLE:
           return '<p>' . t('%capital_name contains terms grouped under parent terms. You can reorganize the terms in %capital_name using their drag-and-drop handles.', array('%capital_name' => drupal_ucfirst($vocabulary->name), '%name' => $vocabulary->name)) . '</p>';
         case TAXONOMY_HIERARCHY_MULTIPLE:
           return '<p>' . t('%capital_name contains terms with multiple parents. Drag and drop of terms with multiple parents is not supported, but you can re-enable drag-and-drop support by editing each term to include only a single parent.', array('%capital_name' => drupal_ucfirst($vocabulary->name))) . '</p>';
+        }
       }
   }
 }