diff --git a/viewtopic.php b/viewtopic.php
index f8d6ca00..b90cb309 100644
--- a/viewtopic.php
+++ b/viewtopic.php
@@ -649,7 +649,7 @@ for($i = 0; $i < $total_posts; $i++)
 {
 	$poster_id        = $postrow[$i]['user_id'];
 	$poster           = ($poster_id == GUEST_UID) ? $lang['GUEST'] : $postrow[$i]['username'];
-	$poster_birthday  = ($poster_id != GUEST_UID) ? date('md', strtotime($postrow[$i]['user_birthday'])) : '';
+	$poster_birthday  = ($poster_id != GUEST_UID && $postrow[$i]['user_birthday'] != '0000-00-00') ? date('md', strtotime($postrow[$i]['user_birthday'])) : '';
 	$post_date        = bb_date($postrow[$i]['post_time'], $bb_cfg['post_date_format']);
 	$max_post_time    = max($max_post_time, $postrow[$i]['post_time']);
 	$poster_posts     = ($poster_id != GUEST_UID) ? $postrow[$i]['user_posts'] : '';