diff --git a/Kwf/Util/Build/Types/Assets.php b/Kwf/Util/Build/Types/Assets.php
index <HASH>..<HASH> 100644
--- a/Kwf/Util/Build/Types/Assets.php
+++ b/Kwf/Util/Build/Types/Assets.php
@@ -198,6 +198,7 @@ class Kwf_Util_Build_Types_Assets extends Kwf_Util_Build_Types_Abstract
 
                     $maxMTime = $p->getMaxMTime(self::$_mimeTypeByExtension[$extension]);
                     foreach ($urls as $urlNum=>$url) {
+                        if (substr($url, 0, 8) != '/assets/') continue;
                         $param = explode('/', $url);
                         $urlLanguage = $param[5];
                         $urlExtension = $param[6];
build only urls from /assets/ in Kwf_Util_Build_Types_Assets

no build needed for external files