diff --git a/scripts/93-backup-tools.sh b/scripts/93-backup-tools.sh
index e6dee95..bf0328a 100644
--- a/scripts/93-backup-tools.sh
+++ b/scripts/93-backup-tools.sh
@@ -248,7 +248,7 @@ cat > "${UNIT_DIR}/mailwolt-backup.timer" <<EOTIM
 Description=MailWolt Backup Timer
 
 [Timer]
-OnCalendar=${BACKUP_ONCALENDAR}
+OnCalendar=${BACKUP_ONCALENDAR:-*-*-* 03:00:00}
 Persistent=true
 
 [Install]