diff --git a/core/modules/language/language.install b/core/modules/language/language.install
index 45d2acb..fe79067 100644
--- a/core/modules/language/language.install
+++ b/core/modules/language/language.install
@@ -15,9 +15,14 @@ function language_update_8001() {
 }
 
 /**
+ * @addtogroup updates-8.4.0
+ * @{
+ */
+
+/**
  * Add the 'include_locked' settings to the 'language_select' widget.
  */
-function language_update_8002() {
+function language_update_8400() {
   foreach (EntityFormDisplay::loadMultiple() as $display_form) {
     $content = $display_form->get('content');
     foreach (array_keys($content) as $element) {
@@ -29,3 +34,7 @@ function language_update_8002() {
     }
   }
 }
+
+/**
+ * @} End of "addtogroup updates-8.4.0".
+ */
diff --git a/core/modules/language/src/Tests/Update/LanguageSelectWidgetUpdateTest.php b/core/modules/language/src/Tests/Update/LanguageSelectWidgetUpdateTest.php
new file mode 100644
index 0000000..05782d7
--- /dev/null
+++ b/core/modules/language/src/Tests/Update/LanguageSelectWidgetUpdateTest.php
@@ -0,0 +1,55 @@
+<?php
+
+namespace Drupal\language\Tests\Update;
+
+use Drupal\system\Tests\Update\UpdatePathTestBase;
+use Drupal\Core\Entity\Entity\EntityFormDisplay;
+
+/**
+ * Tests the update path for the language_select widget.
+ *
+ * @group Update
+ */
+class LanguageSelectWidgetUpdateTest extends UpdatePathTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setDatabaseDumpFiles() {
+    $this->databaseDumpFiles = [
+      __DIR__ . '/../../../../system/tests/fixtures/update/drupal-8.filled.standard.php.gz',
+    ];
+  }
+
+  /**
+   * Tests that language_select widgets are updated.
+   */
+  public function testLanguageUpdate8401() {
+    // Tests before the update.
+    $this->doTestLanguageSelectWidgets([]);
+
+    // Run the update.
+    $this->runUpdates();
+
+    // Tests after the update.
+    $this->doTestLanguageSelectWidgets(['include_locked' => TRUE]);
+  }
+
+  /**
+   * Helper method to test the language_select widgets.
+   *
+   * @param array $expected_settings
+   *   The expected widget settings.
+   */
+  protected function doTestLanguageSelectWidgets($expected_settings) {
+    foreach (EntityFormDisplay::loadMultiple() as $display_form) {
+      $content = $display_form->get('content');
+      foreach (array_keys($content) as $element) {
+        if (isset($content[$element]['type']) && $content[$element]['type'] == 'language_select') {
+          $this->assertEqual($expected_settings, $content[$element]['settings']);
+        }
+      }
+    }
+  }
+
+}