diff --git a/core/includes/form.inc b/core/includes/form.inc
index 49ace44..f97b816 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -3537,7 +3537,7 @@ function form_process_tableselect($element) {
  *       value differs from the element's #default_value.
  *     - source: (optional) The #array_parents of the form element containing
  *       the human-readable name (i.e., as contained in the $form structure) to
- *       use as source for the machine name. Defaults to array('name').
+ *       use as source for the machine name. Defaults to array('label').
  *     - label: (optional) A text to display as label for the machine name value
  *       after the human-readable name form element. Defaults to "Machine name".
  *     - replace_pattern: (optional) A regular expression (without delimiters)
@@ -3570,8 +3570,7 @@ function form_process_machine_name($element, &$form_state) {
   // 'source' only) would leave all other properties undefined, if the defaults
   // were defined in hook_element_info(). Therefore, we apply the defaults here.
   $element['#machine_name'] += array(
-    // @todo Use 'label' by default.
-    'source' => array('name'),
+    'source' => array('label'),
     'target' => '#' . $element['#id'],
     'label' => t('Machine name'),
     'replace_pattern' => '[^a-z0-9_]+',
diff --git a/core/modules/config/tests/config_test/config_test.module b/core/modules/config/tests/config_test/config_test.module
index 44df4da..3e1cbe9 100644
--- a/core/modules/config/tests/config_test/config_test.module
+++ b/core/modules/config/tests/config_test/config_test.module
@@ -214,8 +214,6 @@ function config_test_form($form, &$form_state, ConfigTest $config_test = NULL) {
     '#required' => TRUE,
     '#machine_name' => array(
       'exists' => 'config_test_load',
-      // @todo Update form_process_machine_name() to use 'label' by default.
-      'source' => array('label'),
     ),
   );
   $form['style'] = array(
diff --git a/core/modules/contact/lib/Drupal/contact/CategoryFormController.php b/core/modules/contact/lib/Drupal/contact/CategoryFormController.php
index 37a1aba..9a2f9ba 100644
--- a/core/modules/contact/lib/Drupal/contact/CategoryFormController.php
+++ b/core/modules/contact/lib/Drupal/contact/CategoryFormController.php
@@ -36,7 +36,6 @@ public function form(array $form, array &$form_state, EntityInterface $category)
       '#default_value' => $category->id(),
       '#machine_name' => array(
         'exists' => 'contact_category_load',
-        'source' => array('label'),
       ),
       '#disabled' => !$category->isNew(),
     );
diff --git a/core/modules/filter/filter.admin.inc b/core/modules/filter/filter.admin.inc
index 194a82c..4f56856 100644
--- a/core/modules/filter/filter.admin.inc
+++ b/core/modules/filter/filter.admin.inc
@@ -181,6 +181,7 @@ function filter_admin_format_form($form, &$form_state, $format) {
     '#maxlength' => 255,
     '#machine_name' => array(
       'exists' => 'filter_format_exists',
+      'source' => array('name'),
     ),
     '#disabled' => !empty($format->format),
   );
diff --git a/core/modules/image/image.admin.inc b/core/modules/image/image.admin.inc
index 478f215..ca55227 100644
--- a/core/modules/image/image.admin.inc
+++ b/core/modules/image/image.admin.inc
@@ -59,7 +59,6 @@ function image_style_form($form, &$form_state, $style) {
     '#default_value' => $style->id(),
     '#machine_name' => array(
       'exists' => 'image_style_load',
-      'source' => array('label'),
     ),
     '#required' => TRUE,
   );
@@ -246,7 +245,6 @@ function image_style_add_form($form, &$form_state) {
     '#type' => 'machine_name',
     '#machine_name' => array(
       'exists' => 'image_style_load',
-      'source' => array('label'),
     ),
     '#default_value' => '',
     '#required' => TRUE,
diff --git a/core/modules/node/content_types.inc b/core/modules/node/content_types.inc
index 3450196..a7faa59 100644
--- a/core/modules/node/content_types.inc
+++ b/core/modules/node/content_types.inc
@@ -132,6 +132,7 @@ function node_type_form($form, &$form_state, $type = NULL) {
     '#disabled' => $type->locked,
     '#machine_name' => array(
       'exists' => 'node_type_load',
+      'source' => array('name'),
     ),
     '#description' => t('A unique machine-readable name for this content type. It must only contain lowercase letters, numbers, and underscores. This name will be used for constructing the URL of the %node-add page, in which underscores will be converted into hyphens.', array(
       '%node-add' => t('Add new content'),
diff --git a/core/modules/taxonomy/lib/Drupal/taxonomy/VocabularyFormController.php b/core/modules/taxonomy/lib/Drupal/taxonomy/VocabularyFormController.php
index b791d8b..f6e5110 100644
--- a/core/modules/taxonomy/lib/Drupal/taxonomy/VocabularyFormController.php
+++ b/core/modules/taxonomy/lib/Drupal/taxonomy/VocabularyFormController.php
@@ -37,6 +37,7 @@ public function form(array $form, array &$form_state, EntityInterface $vocabular
       '#maxlength' => 255,
       '#machine_name' => array(
         'exists' => 'taxonomy_vocabulary_machine_name_load',
+        'source' => array('name'),
       ),
     );
     $form['description'] = array(