diff --git a/calendar/inc/class.calendar_groupdav.inc.php b/calendar/inc/class.calendar_groupdav.inc.php
index e70b8e8d00..85ee141df8 100644
--- a/calendar/inc/class.calendar_groupdav.inc.php
+++ b/calendar/inc/class.calendar_groupdav.inc.php
@@ -813,9 +813,8 @@ class calendar_groupdav extends groupdav_handler
 					{
 						$this->groupdav->log(__METHOD__."(,,$user) schedule-tag given, but NO changes for current user events=".array2string($events).', old-event='.array2string($oldEvent));
 					}
-					// we should not return an etag here, as we never store the PUT ical byte-by-byte
-					//header('ETag: "'.$etag.'"');
-					header('Schedule-Tag: "'.$schedule_tag.'"');
+					$this->put_response_headers($eventId, $options['path'], '204 No Content', self::$path_attr == 'caldav_name');
+
 					return '204 No Content';
 				}
 				if ($this->debug && !isset($events)) error_log(__METHOD__."(,,$user) only schedule-tag given for event without participants (only calendar owner) --> handle as regular PUT");
@@ -867,14 +866,6 @@ class calendar_groupdav extends groupdav_handler
 			}
 		}
 
-		if ($this->use_schedule_tag)
-		{
-			$etag = $this->get_etag($cal_id, $schedule_tag);
-			// we should not return an etag here, as we never store the PUT ical byte-by-byte
-			//header('ETag: "'.$etag.'"');
-			header('Schedule-Tag: "'.$schedule_tag.'"');
-		}
-
 		// send evtl. necessary respose headers: Location, etag, ...
 		$this->put_response_headers($cal_id, $options['path'], $retval, self::$path_attr == 'caldav_name');
 
@@ -1315,6 +1306,27 @@ class calendar_groupdav extends groupdav_handler
 		return $etag;
 	}
 
+	/**
+	 * Send response-headers for a PUT (or POST with add-member query parameter)
+	 *
+	 * Reimplemented to send
+	 *
+	 * @param int|array $entry id or array of new created entry
+	 * @param string $path
+	 * @param int|string $retval
+	 * @param boolean $path_attr_is_name=true true: path_attr is ca(l|rd)dav_name, false: id (GroupDAV needs Location header)
+	 */
+	function put_response_headers($entry, $path, $retval, $path_attr_is_name=true)
+	{
+		$etag = $this->get_etag($entry, $schedule_tag);
+
+		if ($this->use_schedule_tag)
+		{
+			header('Schedule-Tag: "'.$schedule_tag.'"');
+		}
+		parent::put_response_headers($entry, $path, $retval, $path_attr_is_name, $etag);
+	}
+
 	/**
 	 * Check if user has the neccessary rights on an event
 	 *
diff --git a/phpgwapi/inc/class.groupdav.inc.php b/phpgwapi/inc/class.groupdav.inc.php
index 17b574b052..739e1397d5 100644
--- a/phpgwapi/inc/class.groupdav.inc.php
+++ b/phpgwapi/inc/class.groupdav.inc.php
@@ -1003,6 +1003,7 @@ class groupdav extends HTTP_WebDAV_Server
 			'DAV:displayname'      => 'Displayname',
 			'DAV:getlastmodified'  => 'Last modified',
 			'DAV:getetag'          => 'ETag',
+			//'CalDAV:schedule-tag'  => 'Schedule-Tag',
 			'DAV:getcontenttype'   => 'Content type',
 			'DAV:resourcetype'     => 'Resource type',
 			//'http://calendarserver.org/ns/:created-by' => 'Created by',
diff --git a/phpgwapi/inc/class.groupdav_handler.inc.php b/phpgwapi/inc/class.groupdav_handler.inc.php
index 43fbe6e87b..2f1094a8ed 100644
--- a/phpgwapi/inc/class.groupdav_handler.inc.php
+++ b/phpgwapi/inc/class.groupdav_handler.inc.php
@@ -474,18 +474,20 @@ abstract class groupdav_handler
 	 * @param string $path
 	 * @param int|string $retval
 	 * @param boolean $path_attr_is_name=true true: path_attr is ca(l|rd)dav_name, false: id (GroupDAV needs Location header)
+	 * @param string $etag=null etag, to not calculate it again (if != null)
 	 */
-	function put_response_headers($entry, $path, $retval, $path_attr_is_name=true)
+	function put_response_headers($entry, $path, $retval, $path_attr_is_name=true, $etag=null)
 	{
 		// we should not return an etag here, as EGroupware never stores ical/vcard byte-by-byte
 		// as SOGO Connector requires ETag header to recognice as successful PUT, we are sending them again for it
 		// --> as all clients dislike not getting an ETag for a PUT, we sending it again even not storing byte-by-byte
 		//if (get_class($this) == 'addressbook_groupdav' && in_array(self::get_agent(),array('thunderbird','lightning')))
 		{
-			header('ETag: "'.$this->get_etag($entry).'"');
+			if (is_null($etag)) $etag = $this->get_etag($entry);
+			header('ETag: "'.$etag.'"');
 		}
-		// send Location header only if we dont use caldav_name as path-attribute or
-		if ($retval !== true && (!$path_attr_is_name ||
+		// send Location header only on success AND if we dont use caldav_name as path-attribute or
+		if (!(is_bool($retval) ? $retval : $retval[0] === '2') && (!$path_attr_is_name ||
 			// POST with add-member query parameter
 			$_SERVER['REQUEST_METHOD'] == 'POST' && isset($_GET['add-member'])))
 		{