diff --git a/lib/classes/calendar/CalendarScheduleModel.php b/lib/classes/calendar/CalendarScheduleModel.php
index 468b7e23842143d45a486cc48dcc8023a6c1ea2e..0aeadee036a02ecc5d47e8d585f3d0c30edf0000 100644
--- a/lib/classes/calendar/CalendarScheduleModel.php
+++ b/lib/classes/calendar/CalendarScheduleModel.php
@@ -623,7 +623,7 @@ class CalendarScheduleModel
                     SET visible = 0
                     WHERE seminar_id = ? AND user_id = ? AND metadate_id = ?");
             } else {
-                $stmt = DBManager::get()->prepare("INSERT INTO schedule_seminare
+                $stmt = DBManager::get()->prepare("INSERT IGNORE INTO schedule_seminare
                     (seminar_id, user_id, metadate_id, visible)
                     VALUES(?, ?, ?, 0)");
             }