diff --git a/tests/HTMLPurifier/AttrDef/LengthTest.php b/tests/HTMLPurifier/AttrDef/LengthTest.php
index 724cda58..0fc5046f 100644
--- a/tests/HTMLPurifier/AttrDef/LengthTest.php
+++ b/tests/HTMLPurifier/AttrDef/LengthTest.php
@@ -1,6 +1,6 @@
 <?php
 
-require_once 'HTMLPurifier/AttrDefHarness.php';
+require_once 'HTMLPurifier/AttrDef/PixelTest.php';
 require_once 'HTMLPurifier/AttrDef/Length.php';
 
 class HTMLPurifier_AttrDef_LengthTest extends HTMLPurifier_AttrDef_PixelsTest