diff --git a/src/CSRF.php b/src/CSRF.php
index 8aa2e1d..bfd8c38 100644
--- a/src/CSRF.php
+++ b/src/CSRF.php
@@ -19,9 +19,9 @@ final class CSRF {
     }
 
     public static function validateRequest(int $tolerance = -1): bool {
-        $token = filter_input(INPUT_POST, '_csrf');
+        $token = (string)filter_input(INPUT_POST, '_csrf');
         if(empty($token))
-            $token = filter_input(INPUT_GET, 'csrf');
+            $token = (string)filter_input(INPUT_GET, 'csrf');
 
         return self::$instance->verifyToken($token, $tolerance);
     }