diff --git a/inc/caldav-PUT-functions.php b/inc/caldav-PUT-functions.php
index 4846e77a..ad533001 100644
--- a/inc/caldav-PUT-functions.php
+++ b/inc/caldav-PUT-functions.php
@@ -384,7 +384,7 @@ function update_scheduling_requests( &$resource ) {
 *
 * Any VEVENTs with the same UID will be concatenated together
 */
-function import_collection( $ics_content, $user_no, $path, $caldav_context ) {
+function import_collection( $ics_content, $user_no, $path, $caldav_context, $appending = false ) {
   global $c, $session, $tz_regex;
 
   if ( ! ini_get('open_basedir') && (isset($c->dbg['ALL']) || isset($c->dbg['put'])) ) {
@@ -400,7 +400,7 @@ function import_collection( $ics_content, $user_no, $path, $caldav_context ) {
   $components = $calendar->GetComponents('VTIMEZONE',false);
 
   $displayname = $calendar->GetPValue('X-WR-CALNAME');
-  if ( isset($displayname) ) {
+  if ( !$appending && isset($displayname) ) {
     $sql = 'UPDATE collection SET dav_displayname = :displayname WHERE dav_name = :dav_name';
     $qry = new AwlQuery( $sql, array( ':displayname' => $displayname, ':dav_name' => $path) );
     if ( ! $qry->Exec('PUT',__LINE__,__FILE__) ) rollback_on_error( $caldav_context, $user_no, $path );
@@ -439,9 +439,11 @@ function import_collection( $ics_content, $user_no, $path, $caldav_context ) {
 
   if ( !(isset($c->skip_bad_event_on_import) && $c->skip_bad_event_on_import) ) $qry->Begin();
   $base_params = array( ':collection_id' => $collection->collection_id );
-  if ( !$qry->QDo('DELETE FROM calendar_item WHERE collection_id = :collection_id', $base_params)
+  if ( !$appending ) {
+    if ( !$qry->QDo('DELETE FROM calendar_item WHERE collection_id = :collection_id', $base_params)
       || !$qry->QDo('DELETE FROM caldav_data WHERE collection_id = :collection_id', $base_params) )
-    rollback_on_error( $caldav_context, $user_no, $collection->collection_id );
+      rollback_on_error( $caldav_context, $user_no, $collection->collection_id );
+  }
 
   $dav_data_insert = <<<EOSQL
 INSERT INTO caldav_data ( user_no, dav_name, dav_etag, caldav_data, caldav_type, logged_user, created, modified, collection_id )
diff --git a/inc/caldav-PUT.php b/inc/caldav-PUT.php
index d3bb4ad2..15840cc5 100644
--- a/inc/caldav-PUT.php
+++ b/inc/caldav-PUT.php
@@ -41,11 +41,13 @@ if ( $dav_resource->IsCollection()  ) {
     return;
   }
 
+  $appending = (isset($_GET['mode']) && $_GET['mode'] == 'append' );
+
   /**
   * CalDAV does not define the result of a PUT on a collection.  We treat that
   * as an import. The code is in caldav-PUT-functions.php
   */
-  import_collection($request->raw_post,$request->user_no,$request->path,true);
+  import_collection($request->raw_post,$request->user_no,$request->path,true, $appending);
   $request->DoResponse( 200 );
   return;
 }