diff --git a/resources/runner/drupal.yml b/resources/runner/drupal.yml
index 76a30588b1ad8b162480d1dbba0e856076739384..a17159c2d250df342855c73e145aee35f7b99e4f 100644
--- a/resources/runner/drupal.yml
+++ b/resources/runner/drupal.yml
@@ -208,7 +208,7 @@ drupal:
         ];
         // Location of the site configuration files.
         $settings['config_sync_directory'] = '../config/sync';
-        $settings['config_readonly'] = FALSE; // !file_exists(getcwd() . '/../disable-config-readonly');
+        $settings['config_readonly'] = !file_exists(getcwd() . '/../disable-config-readonly');
       Testing configuration alters: |
         // The video from the home page interacts with Selenium tests.
         $config['page_manager.page_variant.homepage-layout_builder-0']['variant_settings']['sections'][4]['components']['6ab0ceea-4541-4153-8b64-227e02369d30']['configuration']['text'] = 'Some joinup video';