diff --git a/NEWS b/NEWS
index 37d42853..779d9c26 100644
--- a/NEWS
+++ b/NEWS
@@ -12,6 +12,7 @@ NEWS ( CHANGELOG and HISTORY )                                     HTMLPurifier
 1.5.0, unknown release date
 ! Added a rudimentary I18N and L10N system modeled off MediaWiki
 - Allow 'x' subtag in language codes
+. Added support for IDREF attributes (i.e. for)
 
 1.4.2, unknown release date
 ! docs/enduser-utf8.html explains how to use UTF-8 and HTML Purifier
diff --git a/library/HTMLPurifier/AttrDef/ID.php b/library/HTMLPurifier/AttrDef/ID.php
index 09c277ca..63d30394 100644
--- a/library/HTMLPurifier/AttrDef/ID.php
+++ b/library/HTMLPurifier/AttrDef/ID.php
@@ -39,6 +39,20 @@ HTMLPurifier_ConfigSchema::define(
 class HTMLPurifier_AttrDef_ID extends HTMLPurifier_AttrDef
 {
     
+    /**
+     * Is the ID an actual ID, or a reference to one?
+     * @note IDAccumulator checking is disabled for references
+     * @bool
+     */
+    var $ref = false;
+    
+    /**
+     * @param $ref bool indication if it's ID or IDREF
+     */
+    function HTMLPurifier_AttrDef_ID($ref = false) {
+        $this->ref = $ref;
+    }
+    
     function validate($id, $config, &$context) {
         
         $id = trim($id); // trim it first
@@ -55,8 +69,10 @@ class HTMLPurifier_AttrDef_ID extends HTMLPurifier_AttrDef
                 '%Attr.IDPrefix is set', E_USER_WARNING);
         }
         
-        $id_accumulator =& $context->get('IDAccumulator');
-        if (isset($id_accumulator->ids[$id])) return false;
+        if (!$this->ref) {
+            $id_accumulator =& $context->get('IDAccumulator');
+            if (isset($id_accumulator->ids[$id])) return false;
+        }
         
         // we purposely avoid using regex, hopefully this is faster
         
@@ -71,7 +87,7 @@ class HTMLPurifier_AttrDef_ID extends HTMLPurifier_AttrDef
             $result = ($trim === '');
         }
         
-        if ($result) $id_accumulator->add($id);
+        if (!$this->ref && $result) $id_accumulator->add($id);
         
         // if no change was made to the ID, return the result
         // else, return the new id if stripping whitespace made it
diff --git a/tests/HTMLPurifier/AttrDef/IDTest.php b/tests/HTMLPurifier/AttrDef/IDTest.php
index e47ad9af..7fba690f 100644
--- a/tests/HTMLPurifier/AttrDef/IDTest.php
+++ b/tests/HTMLPurifier/AttrDef/IDTest.php
@@ -74,6 +74,25 @@ class HTMLPurifier_AttrDef_IDTest extends HTMLPurifier_AttrDefHarness
         
     }
     
+    function testIDReference() {
+        
+        $this->def = new HTMLPurifier_AttrDef_ID(true);
+        
+        $this->assertDef('good_id');
+        $this->assertDef('good_id'); // duplicates okay
+        $this->assertDef('<b>', false);
+        
+        $this->def = new HTMLPurifier_AttrDef_ID();
+        
+        $this->assertDef('good_id');
+        $this->assertDef('good_id', false); // duplicate now not okay
+        
+        $this->def = new HTMLPurifier_AttrDef_ID(true);
+        
+        $this->assertDef('good_id'); // reference still okay
+        
+    }
+    
 }
 
 ?>
\ No newline at end of file