diff --git a/NEWS b/NEWS
index bd07f290..8333734c 100644
--- a/NEWS
+++ b/NEWS
@@ -46,6 +46,8 @@ NEWS ( CHANGELOG and HISTORY )                                     HTMLPurifier
 - Fix bug in comment parsing for DirectLex
 - Flush output now displayed when in command line mode for unit tester
 - Fix bug with rgb(0, 1, 2) color syntax with spaces inside shorthand syntax
+- HTMLPurifier_HTMLDefinition->addAttribute can now be called multiple times
+  on the same element without emitting errors.
 . Plugins now get their own changelogs according to project conventions.
 . Convert tokens to use instanceof, reducing memory footprint and
   improving comparison speed.
diff --git a/TODO b/TODO
index cfea5371..6aa5beb2 100644
--- a/TODO
+++ b/TODO
@@ -46,7 +46,6 @@ NICE FEATURES
 
 BUGS
  - Style attribute height/width limiting for images
- - addAttribute multiple calls with HTMLDefinition
  - Support for hard-coded paths/dirname(__FILE__) in include stub and autoload
  - Easy way to blacklist elements and attributes
  - Investigate iconv error emitting
diff --git a/library/HTMLPurifier/HTMLDefinition.php b/library/HTMLPurifier/HTMLDefinition.php
index f8cf093f..360bc4be 100644
--- a/library/HTMLPurifier/HTMLDefinition.php
+++ b/library/HTMLPurifier/HTMLDefinition.php
@@ -87,6 +87,8 @@ class HTMLPurifier_HTMLDefinition extends HTMLPurifier_Definition
     
     /**
      * Adds a custom attribute to a pre-existing element
+     * @note This is strictly convenience, and does not have a corresponding
+     *       method in HTMLPurifier_HTMLModule
      * @param $element_name String element name to add attribute to
      * @param $attr_name String name of attribute
      * @param $def Attribute definition, can be string or object, see
@@ -94,7 +96,11 @@ class HTMLPurifier_HTMLDefinition extends HTMLPurifier_Definition
      */
     public function addAttribute($element_name, $attr_name, $def) {
         $module =& $this->getAnonymousModule();
-        $element =& $module->addBlankElement($element_name);
+        if (!isset($module->info[$element_name])) {
+            $element =& $module->addBlankElement($element_name);
+        } else {
+            $element =& $module->info[$element_name];
+        }
         $element->attr[$attr_name] = $def;
     }
     
diff --git a/tests/HTMLPurifier/HTMLDefinitionTest.php b/tests/HTMLPurifier/HTMLDefinitionTest.php
index b2a03ef9..64e9e1a3 100644
--- a/tests/HTMLPurifier/HTMLDefinitionTest.php
+++ b/tests/HTMLPurifier/HTMLDefinitionTest.php
@@ -85,6 +85,22 @@ a[href|title]
         
     }
     
+    function test_addAttribute_multiple() {
+        
+        $config = HTMLPurifier_Config::create(array(
+            'HTML.DefinitionID' => 'HTMLPurifier_HTMLDefinitionTest->test_addAttribute_multiple'
+        ));
+        $def =& $config->getHTMLDefinition(true);
+        $def->addAttribute('span', 'custom', 'Enum#attribute');
+        $def->addAttribute('span', 'foo', 'Text');
+        
+        $purifier = new HTMLPurifier($config);
+        $input = '<span custom="attribute" foo="asdf">Custom!</span>';
+        $output = $purifier->purify($input);
+        $this->assertIdentical($input, $output);
+        
+    }
+    
     function test_addElement() {
         
         $config = HTMLPurifier_Config::create(array(