diff --git a/library/HTMLPurifier.composer.php b/library/HTMLPurifier.composer.php
index <HASH>..<HASH> 100644
--- a/library/HTMLPurifier.composer.php
+++ b/library/HTMLPurifier.composer.php
@@ -1,4 +1,4 @@
 <?php
 if (!defined('HTMLPURIFIER_PREFIX')) {
-    define('HTMLPURIFIER_PREFIX', __DIR__);
+    define('HTMLPURIFIER_PREFIX', dirname(__FILE__));
 }
Make Composer work with PHP <I> and earlier. Reported by @voku