diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestOptionalContainerForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestOptionalContainerForm.php
index 74cb47c..8a6acdc 100644
--- a/core/modules/system/tests/modules/form_test/src/Form/FormTestOptionalContainerForm.php
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestOptionalContainerForm.php
@@ -26,38 +26,27 @@ public function buildForm(array $form, FormStateInterface $form_state) {
       '#type' => 'container',
       '#attributes' => ['class' => ['empty_optional']],
       '#optional' => TRUE,
-    ];
-    $form['empty_optional']['child'] = [
-      '#type' => 'markup',
-      '#vaule' => ''
+      'child' => ['#markup' => ''],
     ];
     $form['empty_nonoptional'] = [
       '#type' => 'container',
       '#attributes' => ['class' => ['empty_nonoptional']],
       '#optional' => FALSE,
+      'child' => ['#markup' => ''],
     ];
-    $form['empty_nonoptional']['child'] = [
-      '#type' => 'markup',
-      '#vaule' => ''
-    ];
+
     // Non-empty containers
     $form['nonempty_optional'] = [
       '#type' => 'container',
       '#attributes' => ['class' => ['nonempty_optional']],
       '#optional' => TRUE,
-    ];
-    $form['nonempty_optional']['child'] = [
-      '#type' => 'markup',
-      '#vaule' => '<b>nonempty_optional value</b>'
+      'child' => ['#markup' => '<b>nonempty_optional value</b>'],
     ];
     $form['nonempty_nonoptional'] = [
       '#type' => 'container',
       '#attributes' => ['class' => ['nonempty_nonoptional']],
       '#optional' => FALSE,
-    ];
-    $form['nonempty_nonoptional']['child'] = [
-      '#type' => 'markup',
-      '#vaule' => '<b>nonempty_nonoptional value</b>'
+      'child' => ['#markup' => '<b>nonempty_nonoptional value</b>'],
     ];
 
     return $form;