diff --git a/core/lib/Drupal/Core/Render/Element/Container.php b/core/lib/Drupal/Core/Render/Element/Container.php
index 4703c40..23f951a 100644
--- a/core/lib/Drupal/Core/Render/Element/Container.php
+++ b/core/lib/Drupal/Core/Render/Element/Container.php
@@ -13,8 +13,8 @@
  * an HTML ID.
  *
  * Properties:
- * - #optional: Indicates whether the container should not render when it has
- *   no visible children. Defaults to FALSE.
+ * - #optional: Indicates whether the container should render when it has no
+ *   visible children. Defaults to FALSE.
  *
  * Usage example:
  * @code
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 4f60771..7cacf2e 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
@@ -38,14 +38,15 @@ public function buildForm(array $form, FormStateInterface $form_state) {
       '#type' => 'container',
       '#attributes' => ['class' => ['nonempty_optional']],
       '#optional' => TRUE,
-      'child' => [],
     ];
+    $form['nonempty_optional']['child_1'] = [];
+
     $form['nonempty_nonoptional'] = [
       '#type' => 'container',
       '#attributes' => ['class' => ['nonempty_nonoptional']],
       '#optional' => FALSE,
-      'child' => [],
     ];
+    $form['nonempty_nonoptional']['child_2'] = [];
 
     return $form;
   }