diff --git a/library/HTMLPurifier/HTMLDefinition.php b/library/HTMLPurifier/HTMLDefinition.php
index 9f6dff3f..b6e71493 100644
--- a/library/HTMLPurifier/HTMLDefinition.php
+++ b/library/HTMLPurifier/HTMLDefinition.php
@@ -22,9 +22,6 @@ require_once 'HTMLPurifier/TagTransform/Simple.php';
 require_once 'HTMLPurifier/TagTransform/Center.php';
 require_once 'HTMLPurifier/TagTransform/Font.php';
 
-// tweak modules
-require_once 'HTMLPurifier/HTMLModule/TweakSubtractiveWhitelist.php';
-
 // this definition and its modules MUST NOT define configuration directives
 // outside of the HTML or Attr namespaces