diff --git a/phpgwapi/inc/class.ischedule_server.inc.php b/phpgwapi/inc/class.ischedule_server.inc.php
index 7ec8f74210..341ee2ae4c 100644
--- a/phpgwapi/inc/class.ischedule_server.inc.php
+++ b/phpgwapi/inc/class.ischedule_server.inc.php
@@ -362,7 +362,7 @@ class ischedule_server extends groupdav
 	{
 		// parse dkim signature, after unfolding it
 		if (!isset($headers['dkim-signature']) ||
-			!preg_match_all('/[\t\s]*([a-z]+)=([^;]+);?/i',
+			!preg_match_all('/[\t\s]*([a-z]+)\s*=\s*([^;]+);?/i',
 				preg_replace("|\r\n\s+|", "", $headers['dkim-signature']), $matches))
 		{
 			$error = "Can't parse DKIM signature";