diff --git a/src/Request/base.php b/src/Request/base.php
index 62fba8a..c7623cf 100644
--- a/src/Request/base.php
+++ b/src/Request/base.php
@@ -40,8 +40,12 @@ class Base implements RequestInterface
     }
 
     /** @SuppressWarnings(PHPMD.Superglobals) */
-    public function getResp(string $key): string
+    public function getResp(string $key): ?string
     {
+        if (!isset($_REQUEST[$key]))
+        {
+            return null;
+        }
         return $_REQUEST[$key];
     }