diff --git a/phpgwapi/inc/class.vfs_stream_wrapper.inc.php b/phpgwapi/inc/class.vfs_stream_wrapper.inc.php
index 5b65f84e45..41e2eb8963 100644
--- a/phpgwapi/inc/class.vfs_stream_wrapper.inc.php
+++ b/phpgwapi/inc/class.vfs_stream_wrapper.inc.php
@@ -555,7 +555,10 @@ class vfs_stream_wrapper implements iface_stream_wrapper
 		if (!$mime && ($scheme = parse_url($url,PHP_URL_SCHEME)))
 		{
 			// check it it's an eGW stream wrapper returning mime-type via url_stat
-			if (class_exists($class = $scheme.'_stream_wrapper') && ($mime_attr = @constant($class.'::STAT_RETURN_MIME_TYPE')))
+			// we need to first check if the constant is defined, as we get a fatal error in php5.3 otherwise
+			if (class_exists($class = self::scheme2class($scheme)) && 
+				defined($class.'::STAT_RETURN_MIME_TYPE') &&
+				($mime_attr = constant($class.'::STAT_RETURN_MIME_TYPE')))
 			{
 				$stat = call_user_func(array($scheme.'_stream_wrapper','url_stat'),parse_url($url,PHP_URL_PATH),0);
 				if ($stat[$mime_attr])