diff -u b/core/misc/ajax.js b/core/misc/ajax.js
--- b/core/misc/ajax.js
+++ b/core/misc/ajax.js
@@ -291,7 +291,7 @@
     if (event.which === 13 || event.which === 32 && element.type !== 'text' && element.type !== 'textarea' && element.type !== 'tel' && element.type !== 'number') {
       event.preventDefault();
       event.stopPropagation();
-      $(ajax.element_settings.element).trigger(ajax.element_settings.event);
+      $(element).trigger(ajax.element_settings.event);
     }
   };
 
@@ -635,7 +635,7 @@
       element.type !== 'textarea' && element.type !== 'tel' && element.type !== 'number')) {
       event.preventDefault();
       event.stopPropagation();
-      $(element).trigger(ajax.element_settings.event);
+      $(ajax.element_settings.element).trigger(ajax.element_settings.event);
     }
   };
 
diff -u b/core/modules/field_ui/tests/src/FunctionalJavascript/FieldUiIntegrationTest.php b/core/modules/field_ui/tests/src/FunctionalJavascript/FieldUiIntegrationTest.php
--- b/core/modules/field_ui/tests/src/FunctionalJavascript/FieldUiIntegrationTest.php
+++ b/core/modules/field_ui/tests/src/FunctionalJavascript/FieldUiIntegrationTest.php
@@ -30,17 +30,20 @@
     ]);
     $this->drupalLogin($admin_user);
 
-    FieldStorageConfig::create(array(
+    FieldStorageConfig::create([
       'entity_type' => 'user',
       'field_name' => 'field_text_test',
       'type' => 'string',
       'cardinality' => FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED,
-    ))->save();
-    FieldConfig::create(array(
+    ])->save();
+    FieldConfig::create([
       'entity_type' => 'user',
       'field_name' => 'field_text_test',
       'bundle' => 'user',
-    ))->save();
+    ])->save();
+    entity_get_display('user', 'user', 'default')
+      ->setComponent('field_text_test', ['region' => 'content', 'type' => 'string'])
+      ->save();
   }
 
   /**
@@ -50,32 +53,21 @@
   public function testFieldUiFormatterSettingsButtonKeyboardEnter() {
-
     // Get a Field UI manage-display page.
     $this->drupalGet('admin/config/people/accounts/display');
     $session = $this->assertSession();
     $session->statusCodeEquals(200);
     $page = $this->getSession()->getPage();
 
-    // Select a field formatter which has settings, so that the settings button
-    // will appear.
-    // @todo Specify the formatter in setUp() so we can remove this step.
-    $select = $page->findById('edit-fields-field-text-test-type');
-    $select->selectOption('string');
-    $session->assertWaitOnAjaxRequest();
-
-    // We can't know the exact ID of the edit button; it has a random
-    // suffix after the ajax request.
-    $button = $page->find('css', 'input[type=image][id^=edit-fields-field-text-test-settings-edit]');
+    $button = $session->waitForElementVisible('css', 'input[data-drupal-selector=edit-fields-field-text-test-settings-edit]');
     $button->focus();
     $button->keyPress(13); // ENTER key
     $session->assertWaitOnAjaxRequest();
 
     // We expect the edit button has gone.
-    $button = $page->find('css', 'input[type=image][id^=edit-fields-field-text-test-settings-edit]');
+    $button = $page->find('css', 'input[data-drupal-selector=edit-fields-field-text-test-settings-edit]');
     $this->assertTrue(empty($button), 'After pressing field formatter settings button, it should no longer be present.');
 
     // We expect a checkbox for the string formatter's link-to-entity setting.
-    $checkbox = $page->find('css', 'input[id^=edit-fields-field-text-test-settings-edit-form-settings-link-to-entity]');
+    $checkbox = $page->find('css', 'input[data-drupal-selector=edit-fields-field-text-test-settings-edit-form-settings-link-to-entity]');
     $this->assertTrue($checkbox->isVisible(), 'After pressing formatter settings button, formatter settings fields are present.');
   }
-
 }
only in patch2:
unchanged:
--- a/core/misc/ajax.es6.js
+++ b/core/misc/ajax.es6.js
@@ -635,7 +635,7 @@
       element.type !== 'textarea' && element.type !== 'tel' && element.type !== 'number')) {
       event.preventDefault();
       event.stopPropagation();
-      $(ajax.element_settings.element).trigger(ajax.element_settings.event);
+      $(element).trigger(ajax.element_settings.event);
     }
   };