diff --git a/build/service/Updater.php b/build/service/Updater.php
index 99f6bc8..9323f45 100644
--- a/build/service/Updater.php
+++ b/build/service/Updater.php
@@ -43,7 +43,7 @@
 			=========================================================*/
 			foreach($this->config->getDiplomes() as $d_id=>$d_name){
 
-				file_put_contents(__ROOT__."/tmp/$d_id.ics", "BEGIN:VCALENDAR\nVERSION:2.0\nMETHOD:PUBLISH\nX-WR-CALNAME: UPPA $d_name\n");
+				file_put_contents(__ROOT__."/tmp/$d_id.ics", "BEGIN:VCALENDAR\nVERSION:2.0\nPRODID:-//xdrn.io//NONSGML v1.0//EN\nMETHOD:PUBLISH\nX-WR-CALNAME: UPPA $d_name\n");
 
 				/* (1) Browse each date
 				---------------------------------------------------------*/