diff --git a/main/inc/lib/htmlpurifier/library/HTMLPurifier/AttrTransform/SafeEmbed.php b/main/inc/lib/htmlpurifier/library/HTMLPurifier/AttrTransform/SafeEmbed.php
index 38bbdd5f1b..01e9475f8c 100644
--- a/main/inc/lib/htmlpurifier/library/HTMLPurifier/AttrTransform/SafeEmbed.php
+++ b/main/inc/lib/htmlpurifier/library/HTMLPurifier/AttrTransform/SafeEmbed.php
@@ -10,7 +10,7 @@ class HTMLPurifier_AttrTransform_SafeEmbed extends HTMLPurifier_AttrTransform
         $attr['type'] = 'application/x-shockwave-flash';
 
         if (!$config->get('HTML.FlashAllowFullScreen') || !$attr['allowfullscreen'] == 'true') {
-            unset($attr['allowfullscreen']);
+            unset($attr['allowfullscreen']); // if omitted, assume to be 'false'
         }
 
         return $attr;
diff --git a/main/inc/lib/htmlpurifier/library/HTMLPurifier/HTMLModule/SafeEmbed.php b/main/inc/lib/htmlpurifier/library/HTMLPurifier/HTMLModule/SafeEmbed.php
index c99ad97aa6..59114925e5 100644
--- a/main/inc/lib/htmlpurifier/library/HTMLPurifier/HTMLModule/SafeEmbed.php
+++ b/main/inc/lib/htmlpurifier/library/HTMLPurifier/HTMLModule/SafeEmbed.php
@@ -11,23 +11,20 @@ class HTMLPurifier_HTMLModule_SafeEmbed extends HTMLPurifier_HTMLModule
     public function setup($config) {
 
         $max = $config->get('HTML.MaxImgLength');
-        $attr = array(
+        $embed = $this->addElement(
+            'embed', 'Inline', 'Empty', 'Common',
+            array(
                 'src*' => 'URI#embedded',
                 'type' => 'Enum#application/x-shockwave-flash',
                 'width' => 'Pixels#' . $max,
                 'height' => 'Pixels#' . $max,
                 'allowscriptaccess' => 'Enum#never',
                 'allownetworking' => 'Enum#internal',
+                'allowfullscreen' => 'Enum#true,false',
                 'flashvars' => 'Text',
-                'wmode' => 'Enum#window,transparent,opaque',
+                'wmode' => 'Enum#window',
                 'name' => 'ID',
-        );
-        if ($config->get('HTML.FlashAllowFullScreen')) {
-            $attr['allowfullscreen'] = 'Enum#true,false';
-        }
-
-        $embed = $this->addElement(
-            'embed', 'Inline', 'Empty', 'Common', $attr
+            )
         );
         $embed->attr_transform_post[] = new HTMLPurifier_AttrTransform_SafeEmbed();