diff --git a/symfony/framework-bundle/3.3/public/index.php b/symfony/framework-bundle/3.3/public/index.php
index e173fb9d..10878ce5 100644
--- a/symfony/framework-bundle/3.3/public/index.php
+++ b/symfony/framework-bundle/3.3/public/index.php
@@ -16,7 +16,7 @@ if (!isset($_SERVER['APP_ENV'])) {
 }
 
 $env = $_SERVER['APP_ENV'] ?? 'dev';
-$debug = (bool) $_SERVER['APP_DEBUG'] ?? ('prod' !== $env);
+$debug = (bool) ($_SERVER['APP_DEBUG'] ?? ('prod' !== $env));
 
 if ($debug) {
     umask(0000);