diff --git a/src/Data/Course.php b/src/Data/Course.php
index a91ca20..8bca6d6 100644
--- a/src/Data/Course.php
+++ b/src/Data/Course.php
@@ -15,7 +15,7 @@ class Course extends Data
         public int $id,
 
         #[MapInputName('bausteinId')]
-        public string $courseId,
+        public int $courseId,
 
         #[MapInputName('veranstalter')]
         public string $organizer,