diff --git a/tests/HTMLPurifier/AttrDef/CompositeTest.php b/tests/HTMLPurifier/AttrDef/CompositeTest.php
index adc520a2..c2ac8319 100644
--- a/tests/HTMLPurifier/AttrDef/CompositeTest.php
+++ b/tests/HTMLPurifier/AttrDef/CompositeTest.php
@@ -6,6 +6,7 @@ class HTMLPurifier_AttrDef_Composite_Testable extends
       HTMLPurifier_AttrDef_Composite
 {
     
+    // we need to pass by ref to get the mocks in
     function HTMLPurifier_AttrDef_Composite_Testable(&$defs) {
         $this->defs =& $defs;
     }