diff --git a/src/Illuminate/Support/Carbon.php b/src/Illuminate/Support/Carbon.php
index 6ac3aa0de6b7..170e48895a78 100644
--- a/src/Illuminate/Support/Carbon.php
+++ b/src/Illuminate/Support/Carbon.php
@@ -52,7 +52,7 @@ public static function serializeUsing($callback)
      * @param  array  $array
      * @return static
      */
-    public static function __set_state($array)
+    public static function __set_state(array $array)
     {
         return static::instance(parent::__set_state($array));
     }