diff --git a/src/Helper/StringHelper.php b/src/Helper/StringHelper.php
index a4c409d..d60a808 100644
--- a/src/Helper/StringHelper.php
+++ b/src/Helper/StringHelper.php
@@ -13,10 +13,10 @@
  *
  * @see StringHelperTest
  */
-final class StringHelper
+final readonly class StringHelper
 {
     public function __construct(
-        private readonly SluggerInterface $slugger
+        private SluggerInterface $slugger
     ) {
     }