diff -up lib/Sabre/autoload.php.orig lib/Sabre/autoload.php
--- lib/Sabre/autoload.php.orig	2014-05-22 09:19:59.914874236 +0200
+++ lib/Sabre/autoload.php	2014-05-22 09:21:26.300242963 +0200
@@ -15,11 +15,9 @@
  * @license http://sabre.io/license/ Modified BSD License
  */
 
-/**
- * We are assuming that the composer autoloader is just 2 directories up.
- *
- * This is not the case when sabredav is installed as a dependency. But, in
- * those cases it's not expected that people will look for this file anyway.
- */
-
-require __DIR__ . '/../../vendor/autoload.php';
+spl_autoload_register(function ($class) {
+    if (strpos($class,'Sabre\\')===0) {
+        $file = __DIR__ . str_replace('\\', '/', substr($class,5)).'.php';
+        @include $file;
+    }
+});