diff --git a/core/modules/taxonomy/taxonomy.admin.inc b/core/modules/taxonomy/taxonomy.admin.inc
index cabd05e..a95b856 100644
--- a/core/modules/taxonomy/taxonomy.admin.inc
+++ b/core/modules/taxonomy/taxonomy.admin.inc
@@ -152,10 +152,6 @@ function taxonomy_form_vocabulary($form, &$form_state, TaxonomyVocabulary $vocab
       'exists' => 'taxonomy_vocabulary_machine_name_load',
     ),
   );
-  $form['old_machine_name'] = array(
-    '#type' => 'value',
-    '#value' => $vocabulary->machine_name,
-  );
   $form['description'] = array(
     '#type' => 'textfield',
     '#title' => t('Description'),
diff --git a/core/modules/taxonomy/taxonomy.entity.inc b/core/modules/taxonomy/taxonomy.entity.inc
index e1f7db8..f0e386d 100644
--- a/core/modules/taxonomy/taxonomy.entity.inc
+++ b/core/modules/taxonomy/taxonomy.entity.inc
@@ -32,21 +32,22 @@ class TaxonomyTerm extends Entity {
   public $name;
 
   /**
-   * Description of the term.
+   * (optional) Description of the term.
    *
    * @var string
    */
   public $description;
 
   /**
-   * The text format name for the term's description.
+   * (optional) The text format name for the term's description.
    *
    * @var string
    */
   public $format;
 
   /**
-   * The weight of this term in relation to other terms of the same vocabulary.
+   * (optional) The weight of this term in relation to other terms of the same
+   * vocabulary.
    *
    * @var integer
    */
@@ -65,6 +66,15 @@ class TaxonomyTerm extends Entity {
    * @var array
    */
   public $parent;
+
+  /**
+   * (optional) The machine name of the vocabulary the term is assigned to. If
+   * not given, this value will be set automatically by loading the vocabulary
+   * based on the $entity->vid property.
+   *
+   * @var string
+   */
+  public $vocabulary_machine_name;
 }
 
 /**
@@ -229,7 +239,7 @@ class TaxonomyVocabulary extends Entity {
   public $machine_name;
 
   /**
-   * Description of the vocabulary.
+   * (optional) Description of the vocabulary.
    *
    * @var string
    */
@@ -248,11 +258,18 @@ class TaxonomyVocabulary extends Entity {
   public $hierarchy = TAXONOMY_HIERARCHY_DISABLED;
 
   /**
-   * The weight of this vocabulary in relation to other vocabularies.
+   * (optional) The weight of this vocabulary in relation to other vocabularies.
    *
    * @var integer
    */
   public $weight = 0;
+
+  /**
+   * (optional) The original vocabulary instance loaded prior to saving.
+   *
+   * @var EntityInterface
+   */
+  public $original;
 }
 
 /**