diff --git a/src/Form/Model/ParticipantDto.php b/src/Form/Model/ParticipantDto.php
index eb42fc7..09d7dd1 100644
--- a/src/Form/Model/ParticipantDto.php
+++ b/src/Form/Model/ParticipantDto.php
@@ -74,7 +74,10 @@ class ParticipantDto
 
     public array $courses = [];
     public array $additionalServices = [];
+
+    #[Assert\NotNull(message: 'Bitte auswählen', groups: ['booking_edit', 'booking_create_step_2'])]
     public ?Service $skiPass = null;
+
     public array $board = [];
     public array $rentals = [];
     public ?Service $rentalInsurance = null;