diff --git a/src/Error/ErrorValue.php b/src/Error/ErrorValue.php
index aa58cd3..865c107 100644
--- a/src/Error/ErrorValue.php
+++ b/src/Error/ErrorValue.php
@@ -18,7 +18,7 @@ final private function __construct(
     ) {
     }
 
-    public static function of(string $code, string $message): static
+    final public static function of(string $code, string $message): static
     {
         return new static($code, $message);
     }