diff --git a/core/lib/Drupal/Core/EventSubscriber/MainContentViewSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/MainContentViewSubscriber.php
index 0617064..f98fb71 100644
--- a/core/lib/Drupal/Core/EventSubscriber/MainContentViewSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/MainContentViewSubscriber.php
@@ -49,7 +49,7 @@ class MainContentViewSubscriber implements EventSubscriberInterface {
   protected $mainContentRenderers;
 
   /**
-   * Url query attribute to indicate the wrapper used to render a request.
+   * URL query attribute to indicate the wrapper used to render a request.
    *
    * This controls wrapping the HTML content for example in a modal dialog.
    */
@@ -84,7 +84,8 @@ public function onViewRenderArray(GetResponseForControllerResultEvent $event) {
     // Render the controller result into a response if it's a render array.
     if (is_array($result) && ($request->query->has(static::WRAPPER_ENVELOPE) || $request->getRequestFormat() == 'html')) {
       $wrapper = $request->query->get(static::WRAPPER_ENVELOPE, 'html');
-      // Fall back on HTML if we don't have a renderer.
+
+      // Fall back to HTML if the requested wrapper envelope is not available.
       $wrapper = isset($this->mainContentRenderers[$wrapper]) ? $wrapper : 'html';
 
       $renderer = $this->classResolver->getInstanceFromDefinition($this->mainContentRenderers[$wrapper]);