diff --git a/modules/comment/comment.module b/modules/comment/comment.module
index a83069f..90dda4b 100644
--- a/modules/comment/comment.module
+++ b/modules/comment/comment.module
@@ -2068,7 +2068,12 @@ function comment_preview($comment) {
 
   if (!form_get_errors()) {
     $comment_body = field_get_items('comment', $comment, 'comment_body');
-    $comment->format = $comment_body[0]['format'];
+	if (!empty($comment_body[0]['format'])) {
+      $comment->format = $comment_body[0]['format'];
+	}
+	else {
+	  $comment->format = 'plain_text';
+	}
     // Attach the user and time information.
     if (!empty($comment->name)) {
       $account = user_load_by_name($comment->name);