diff --git a/core/tests/Drupal/KernelTests/Core/Asset/AttachedAssetsTest.php b/core/tests/Drupal/KernelTests/Core/Asset/AttachedAssetsTest.php
index bee5399..76445fe 100644
--- a/core/tests/Drupal/KernelTests/Core/Asset/AttachedAssetsTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Asset/AttachedAssetsTest.php
@@ -202,6 +202,8 @@ function testSettings() {
     $endToken = '}';
     $start = strpos($rendered_js, $startToken);
     $end = strrpos($rendered_js, $endToken);
+    // Convert to a string, as $renderer_js is a \Drupal\Core\Render\Markup
+    // object.
     $json  = Unicode::substr((string) $rendered_js, $start, $end - $start + 1);
     $parsed_settings = Json::decode($json);