diff --git a/core/lib/Drupal/Core/Render/ReadOnlyRenderArray.php b/core/lib/Drupal/Core/Render/ReadOnlyRenderArray.php
index ac03a32..b17a680 100644
--- a/core/lib/Drupal/Core/Render/ReadOnlyRenderArray.php
+++ b/core/lib/Drupal/Core/Render/ReadOnlyRenderArray.php
@@ -10,6 +10,16 @@
 class ReadOnlyRenderArray extends \ArrayObject implements RenderableInterface {
 
   /**
+   * ReadOnlyRenderArray constructor.
+   *
+   * @param array $input
+   *   The render array to wrap into a read-only object.
+   */
+  public function __construct(array $input = []) {
+    parent::__construct($input, 0, RenderArrayIterator::class);
+  }
+
+  /**
    * {@inheritdoc}
    */
   public function toRenderable() {
@@ -17,6 +27,18 @@ public function toRenderable() {
   }
 
   /**
+   * Magic getter since Twig sometimes tries to access properties.
+   *
+   * @param mixed $index
+   *   The index with the value.
+   *
+   * @return \Drupal\Core\Render\ReadOnlyRenderArray|mixed
+   */
+  public function __get($index) {
+    return $this->offsetGet($index);
+  }
+
+  /**
    * {@inheritdoc}
    */
   public function offsetGet($index) {