diff --git includes/menu.inc includes/menu.inc
index 5be5b11..7957302 100644
--- includes/menu.inc
+++ includes/menu.inc
@@ -602,6 +602,10 @@ function _menu_check_access(&$item, $map) {
     }
     elseif (function_exists($callback)) {
       $item['access'] = call_user_func_array($callback, $arguments);
+      if (!isset($item['access'])) {
+        watchdog('menu.inc',"Access callback function $callback failed to return a value when called with arguments " . var_export($arguments,1),WATCHDOG_WARNING,'http://drupal.org/node/994992');
+        $item['access'] = FALSE;
+      }
     }
   }
 }