diff --git a/src/Grant/PasswordGrant.php b/src/Grant/PasswordGrant.php
index 03113146..053a3fc9 100644
--- a/src/Grant/PasswordGrant.php
+++ b/src/Grant/PasswordGrant.php
@@ -38,7 +38,7 @@ class PasswordGrant extends AbstractGrant
 
     /**
      * Callback to authenticate a user's name and password
-     * @var function
+     * @var callable
      */
     protected $callback;