diff --git a/htdocs/user/notify/card.php b/htdocs/user/notify/card.php
index 4ef62f25ab5..3acad0ac0c3 100644
--- a/htdocs/user/notify/card.php
+++ b/htdocs/user/notify/card.php
@@ -437,7 +437,7 @@ if ($result > 0) {
 	}
 
 	print '<form method="post" action="'.$_SERVER["PHP_SELF"].'" name="formfilter">';
-	if (!empty($optioncss)) {
+	if (isset($optioncss) && $optioncss != '') {
 		print '<input type="hidden" name="optioncss" value="'.$optioncss.'">';
 	}
 	print '<input type="hidden" name="token" value="'.newToken().'">';