diff -u b/render_example/src/Controller/RenderExampleController.php b/render_example/src/Controller/RenderExampleController.php
--- b/render_example/src/Controller/RenderExampleController.php
+++ b/render_example/src/Controller/RenderExampleController.php
@@ -66,7 +66,7 @@
 
     // CSS and JavaScript libraries can be attached to elements in a renderable
     // array. This way, if the element ends up being rendered and displayed you
-    // know for sure the CSS/JavaScript will also be included. But, if the for
+    // know for sure the CSS/JavaScript will also be included. But, if for
     // some reason the element isn't ever rendered then Drupal can skip the
     // unnecessary extra files.
     //
@@ -293,7 +293,7 @@
     // in addition to functions. See
     // \Drupal\render_example\Controller\RenderExampleController::preRender()
     // @todo: This doesn't work, we need to fix it.
-    // $build['#pre_render'] = [static::class . '::preRender'];
+    // $build['#pre_render'] = [static::class, 'preRender'];
 
     // Caching is an important part of the Render API, converting an array to a
     // string of HTML can be an expensive process, and therefore whenever