diff --git a/src/Bundle/ChillPersonBundle/Export/Filter/AccompanyingCourseFilters/ReferrerFilterBetweenDates.php b/src/Bundle/ChillPersonBundle/Export/Filter/AccompanyingCourseFilters/ReferrerFilterBetweenDates.php
index 33a9b4cc3..c58aad3bb 100644
--- a/src/Bundle/ChillPersonBundle/Export/Filter/AccompanyingCourseFilters/ReferrerFilterBetweenDates.php
+++ b/src/Bundle/ChillPersonBundle/Export/Filter/AccompanyingCourseFilters/ReferrerFilterBetweenDates.php
@@ -30,7 +30,7 @@ use Symfony\Component\Form\FormBuilderInterface;
  *
  * @see ReferrerFilterBetweenDatesTest for tests
  */
-class ReferrerFilterBetweenDates implements FilterInterface
+final readonly class ReferrerFilterBetweenDates implements FilterInterface
 {
     private const A = 'acp_referrer_filter_uhistory';
 
@@ -40,7 +40,7 @@ class ReferrerFilterBetweenDates implements FilterInterface
     private const PU = 'acp_referrer_filter_users';
 
     public function __construct(
-        private readonly RollingDateConverterInterface $rollingDateConverter,
+        private RollingDateConverterInterface $rollingDateConverter,
         private UserRender $userRender
     ) {
     }