diff --git a/wp-includes/comment-template.php b/wp-includes/comment-template.php
index e4840eab0f..dd74060129 100644
--- a/wp-includes/comment-template.php
+++ b/wp-includes/comment-template.php
@@ -738,8 +738,13 @@ function pings_open( $post_id = NULL ) {
  */
 function wp_comment_form_unfiltered_html_nonce() {
 	global $post;
+
+	$post_id = 0;
+	if ( !empty($post) )
+		$post_id = $post->ID;
+
 	if ( current_user_can('unfiltered_html') )
-		wp_nonce_field('unfiltered-html-comment_' . $post->ID, '_wp_unfiltered_html_comment', false);
+		wp_nonce_field('unfiltered-html-comment_' . $post_id, '_wp_unfiltered_html_comment', false);
 }
 
 /**