diff --git a/NEWS b/NEWS
index af32f72f..5906e9db 100644
--- a/NEWS
+++ b/NEWS
@@ -37,6 +37,7 @@ NEWS ( CHANGELOG and HISTORY )                                     HTMLPurifier
   prefixes first and then the literal module
 - Empty strings get converted to empty arrays instead of arrays with
   an empty string in them.
+- Merging in attribute lists now works.
 . Demo script removed: it has been added to the website's repository
 . Basic.php script modified to work out of the box
 . Refactor AttrTransform classes to reduce duplication
diff --git a/library/HTMLPurifier/ElementDef.php b/library/HTMLPurifier/ElementDef.php
index 21bc5f36..73c94abe 100644
--- a/library/HTMLPurifier/ElementDef.php
+++ b/library/HTMLPurifier/ElementDef.php
@@ -95,7 +95,7 @@ class HTMLPurifier_ElementDef
         
         // later keys takes precedence
         foreach($def->attr as $k => $v) {
-            if ($k == 0) {
+            if ($k === 0) {
                 // merge in the includes
                 // sorry, no way to override an include
                 foreach ($v as $v2) {
diff --git a/library/HTMLPurifier/HTMLModuleManager.php b/library/HTMLPurifier/HTMLModuleManager.php
index 8860f68c..81ef13a5 100644
--- a/library/HTMLPurifier/HTMLModuleManager.php
+++ b/library/HTMLPurifier/HTMLModuleManager.php
@@ -225,14 +225,14 @@ class HTMLPurifier_HTMLModuleManager
             $ok = false;
             foreach ($this->prefixes as $prefix) {
                 $module = $prefix . $original_module;
-                if (class_exists($module)) {
+                if ($this->_classExists($module)) {
                     $ok = true;
                     break;
                 }
             }
             if (!$ok) {
                 $module = $original_module;
-                if (!class_exists($module, false)) {
+                if (!$this->_classExists($module)) {
                     trigger_error($original_module . ' module does not exist',
                         E_USER_ERROR);
                     return;
@@ -247,6 +247,23 @@ class HTMLPurifier_HTMLModuleManager
         }
     }
     
+    /**
+     * Safely tests for class existence without invoking __autoload in PHP5
+     * @param $name String class name to test
+     * @private
+     */
+    function _classExists($name) {
+        static $is_php_4 = null;
+        if ($is_php_4 === null) {
+            $is_php_4 = version_compare(PHP_VERSION, '5', '<');
+        }
+        if ($is_php_4) {
+            return class_exists($name);
+        } else {
+            return class_exists($name, false);
+        }
+    }
+    
     /**
      * Makes a collection active, while also making it valid if not
      * already done so. See $activeModules for the semantics of "active".
@@ -508,7 +525,8 @@ class HTMLPurifier_HTMLModuleManager
         
         $elements = array();
         foreach ($this->activeModules as $module) {
-            foreach ($module->elements as $name) {
+            foreach ($module->info as $name => $v) {
+                if (isset($elements[$name])) continue;
                 $elements[$name] = $this->getElement($name, $config);
             }
         }