diff --git a/src/MiddlewarePipe.php b/src/MiddlewarePipe.php
index 1b0bf88..470674a 100644
--- a/src/MiddlewarePipe.php
+++ b/src/MiddlewarePipe.php
@@ -49,7 +49,7 @@ class MiddlewarePipe implements ServerMiddlewareInterface
     /**
      * @var Response
      */
-    private $responsePrototype;
+    protected $responsePrototype;
 
     /**
      * Constructor