diff --git a/core/modules/field/field.api.php b/core/modules/field/field.api.php
index 69741a123e..44331500d8 100644
--- a/core/modules/field/field.api.php
+++ b/core/modules/field/field.api.php
@@ -262,8 +262,12 @@ function hook_field_widget_WIDGET_TYPE_form_alter(&$element, \Drupal\Core\Form\F
  * @see hook_field_widget_multiple_WIDGET_TYPE_form_alter()
  */
 function hook_field_widget_multiple_form_alter(array &$elements, \Drupal\Core\Form\FormStateInterface $form_state, array $context) {
-  // Add a css class to the overall element of any widget.
-  $elements['#attributes']['class'][] = 'myclass';
+  // Add a css class to widget form elements for all fields of type mytype.
+  $field_definition = $context['items']->getFieldDefinition();
+  if ($field_definition->getType() == 'mytype') {
+    // Be sure not to overwrite existing attributes.
+    $elements['#attributes']['class'][] = 'myclass';
+  }
 }
 
 /**
@@ -290,18 +294,13 @@ function hook_field_widget_multiple_form_alter(array &$elements, \Drupal\Core\Fo
  * @see hook_field_widget_multiple_form_alter()
  */
 function hook_field_widget_multiple_WIDGET_TYPE_form_alter(array &$elements, \Drupal\Core\Form\FormStateInterface $form_state, array $context) {
-  // Alter the overall title for the multivalue widget (the table header,
-  // above the rows).
-  $elements['#title'] = t('Review your %title entries', ['%title' => $elements['#title']]);
-
-  if (!empty($elements['#description'])) {
-    // Add a paragraph to the description, above all the rows.
-    $elements['#description'] = [
-      '#markup' => $elements['#description'],
-    ];
-  }
-  else {
-    $elements['#description'] = t('These items might be out of date.');
+  // Code here will only act on widgets of type WIDGET_TYPE. For example,
+  // hook_field_widget_mymodule_autocomplete_form_alter() will only act on
+  // widgets of type 'mymodule_autocomplete'.
+  // Change the autcomplete route for each autocomplete element within the
+  // multivalue widget.
+  foreach (Element::children($elements) as $delta => $element) {
+    $elements[$delta]['#autocomplete_route_name'] = 'mymodule.autocomplete_route';
   }
 }
 
diff --git a/core/modules/field/tests/modules/field_test/field_test.module b/core/modules/field/tests/modules/field_test/field_test.module
index 9121e942ea..15f8708adf 100644
--- a/core/modules/field/tests/modules/field_test/field_test.module
+++ b/core/modules/field/tests/modules/field_test/field_test.module
@@ -101,15 +101,6 @@ function field_test_entity_display_build_alter(&$output, $context) {
  */
 function field_test_field_widget_form_alter(&$element, FormStateInterface $form_state, $context) {
   $field_definition = $context['items']->getFieldDefinition();
-  switch ($field_definition->getName()) {
-    case 'alter_test_text':
-      drupal_set_message('Field size: ' . $context['widget']->getSetting('size'));
-      break;
-
-    case 'alter_test_options':
-      drupal_set_message('Widget type: ' . $context['widget']->getPluginId());
-      break;
-  }
   // Set a message if this is for the form displayed to set default value for
   // the field.
   if ($context['default']) {