diff --git a/src/helpers.php b/src/helpers.php
index 6482eca4..a7aa7a86 100644
--- a/src/helpers.php
+++ b/src/helpers.php
@@ -40,7 +40,7 @@ if (!function_exists('config')) {
      */
     function config($key = null, $default = null)
     {
-        if (is_null($key)) {
+        if ($key === null) {
             return Config::getItems();
         }