diff --git a/src/League/OAuth2/Server/Storage/Fluent/Client.php b/src/League/OAuth2/Server/Storage/Fluent/Client.php
index b8adeb0a..cf0544d3 100644
--- a/src/League/OAuth2/Server/Storage/Fluent/Client.php
+++ b/src/League/OAuth2/Server/Storage/Fluent/Client.php
@@ -7,7 +7,7 @@ use \League\OAuth2\Server\Storage\ClientInterface;
 
 class Client implements ClientInterface {
 
-    public function getClient($clientId, $clientSecret = null, $redirectUri = null, $grantType)
+    public function getClient($clientId, $clientSecret = null, $redirectUri = null, $grantType = null)
     {
         if ( ! is_null($redirectUri) && is_null($clientSecret)) {
             $result = DB::table('oauth_clients')
@@ -41,4 +41,4 @@ class Client implements ClientInterface {
         );
     }
 
-}
\ No newline at end of file
+}