diff --git a/icalsrv.php b/icalsrv.php
index 882a6052a9..2d465c3263 100644
--- a/icalsrv.php
+++ b/icalsrv.php
@@ -560,6 +560,9 @@
 		$content_type = 'text/calendar';
 		if($content_type)
 		{
+			header('Last-Modified: '.gmdate('D, d M Y H:i:s') . ' GMT');
+			header('Cache-Control: no-store, no-cache, must-revalidate'); // HTTP/1.1
+			header('Cache-Control: pre-check=0, post-check=0, max-age=0'); // HTTP/1.1
 			header('Content-Type: '.$content_type);
 		}
 		echo $vcalstr;