diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index dc36c4526e5dbbb614c27ad84021c0d4d88b6abc..3101e1bc850fbde981dd90cf17382c75625efb14 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -894,7 +894,7 @@ function watchdog($type, $message, array $variables = array(), $severity = WATCH
  * @see theme_status_messages()
  */
 function drupal_set_message($message = NULL, $type = 'status', $repeat = FALSE) {
-  if ($message) {
+  if (isset($message)) {
     if (!isset($_SESSION['messages'][$type])) {
       $_SESSION['messages'][$type] = array();
     }