diff --git a/internal/server/api.go b/internal/server/api.go
index f8dd951..5514ad3 100644
--- a/internal/server/api.go
+++ b/internal/server/api.go
@@ -524,7 +524,7 @@ func (h *APIHandlers) GetTrainingDateAttendeeCount(ctx context.Context, req GetT
 
 func (h *APIHandlers) DeleteTrainingDateAttendee(ctx context.Context, req DeleteTrainingDateAttendeeRequestObject) (DeleteTrainingDateAttendeeResponseObject, error) {
 	err := h.trainingDateAttendeeRepository.Delete(req.TrainingDateAttendeeID)
-	if err == training.ErrTrainingDateAttendeeNotFound {
+	if errors.Is(err, training.ErrTrainingDateAttendeeNotFound) {
 		return DeleteTrainingDateAttendee404ApplicationProblemPlusJSONResponse{
 			NotFoundErrorApplicationProblemPlusJSONResponse: NotFoundErrorApplicationProblemPlusJSONResponse{
 				Status: fiber.StatusNotFound,