diff --git a/server/vbv_lernwelt/sso/admin.py b/server/vbv_lernwelt/sso/admin.py
index 01d57e66..1db24124 100644
--- a/server/vbv_lernwelt/sso/admin.py
+++ b/server/vbv_lernwelt/sso/admin.py
@@ -40,12 +40,12 @@ def sync_sso_roles_from_admin(user: User, request):
         for csu in CourseSessionUser.objects.filter(user=user)
     }
 
-    course_roles += {
+    course_roles.update(
         (relation.participant.course_session.course.slug, "LEARNING_MENTOR")
         for relation in AgentParticipantRelation.objects.filter(
             agent=user, role=AgentParticipantRoleType.LEARNING_MENTOR.value
         )
-    }
+    )
 
     for csg in CourseSessionGroup.objects.filter(supervisor=user):
         for course_session in csg.course_session.all():