diff --git a/library/HTMLPurifier/HTMLDefinition.php b/library/HTMLPurifier/HTMLDefinition.php
index b182b083..7ca086a9 100644
--- a/library/HTMLPurifier/HTMLDefinition.php
+++ b/library/HTMLPurifier/HTMLDefinition.php
@@ -72,7 +72,7 @@ HTMLPurifier_ConfigSchema::define(
     'can overload it with your own list of tags to allow.  Note that this '.
     'method is subtractive: it does its job by taking away from HTML Purifier '.
     'usual feature set, so you cannot add a tag that HTML Purifier never '.
-    'supported in the first place (like embed).  If you change this, you '.
+    'supported in the first place (like embed, form or head).  If you change this, you '.
     'probably also want to change %HTML.AllowedAttributes. '.
     '<strong>Warning:</strong> If another directive conflicts with the '.
     'elements here, <em>that</em> directive will win and override. '.
@@ -561,9 +561,9 @@ class HTMLPurifier_HTMLDefinition
         
         //////////////////////////////////////////////////////////////////////
         // %HTML.Allowed(Elements|Attributes) : cut non-allowed elements
+        
         $allowed_elements = $config->get('HTML', 'AllowedElements');
         if (is_array($allowed_elements)) {
-            // $allowed_elements[$this->info_parent] = true; // allow parent element
             foreach ($this->info as $name => $d) {
                 if(!isset($allowed_elements[$name])) unset($this->info[$name]);
             }
diff --git a/library/HTMLPurifier/Strategy/FixNesting.php b/library/HTMLPurifier/Strategy/FixNesting.php
index 9ae614e8..dd5a920f 100644
--- a/library/HTMLPurifier/Strategy/FixNesting.php
+++ b/library/HTMLPurifier/Strategy/FixNesting.php
@@ -156,11 +156,14 @@ class HTMLPurifier_Strategy_FixNesting extends HTMLPurifier_Strategy
                     
                 }
                 
-                $child_def = $def->child;
-                
-                // have DTD child def validate children
-                $result = $child_def->validateChildren(
-                    $child_tokens, $config, $context);
+                if (!empty($def->child)) {
+                    // have DTD child def validate children
+                    $result = $def->child->validateChildren(
+                        $child_tokens, $config, $context);
+                } else {
+                    // weird, no child definition, get rid of everything
+                    $result = false;
+                }
                 
                 // determine whether or not this element has any exclusions
                 $excludes = $def->excludes;