diff --git a/src/App/src/Middleware/ContentNegotiationMiddleware.php b/src/App/src/Middleware/ContentNegotiationMiddleware.php
index 23b0a99..f56a192 100644
--- a/src/App/src/Middleware/ContentNegotiationMiddleware.php
+++ b/src/App/src/Middleware/ContentNegotiationMiddleware.php
@@ -30,7 +30,7 @@ class ContentNegotiationMiddleware implements MiddlewareInterface
         "config.content-negotiation",
     )]
     public function __construct(
-        private array $config,
+        private readonly array $config,
     ) {
     }