diff --git a/src/Oauth2/Authentication/Server.php b/src/Oauth2/Authentication/Server.php
index 107fa387..6125fb02 100644
--- a/src/Oauth2/Authentication/Server.php
+++ b/src/Oauth2/Authentication/Server.php
@@ -179,7 +179,7 @@ maintenance of the server.',
 
             // Ensure response type is one that is recognised
             if ( ! in_array($params['response_type'], 
-                $this->config['response_types'])) {
+                $this->response_types)) {
 
                 throw new OAuthServerClientException(
                     $this->errors['unsupported_response_type'], 3);
@@ -364,8 +364,7 @@ maintenance of the server.',
                 $authParams['grant_type'] : $_POST['grant_type'];
 
             // Ensure response type is one that is recognised
-            if ( ! in_array($params['response_type'],
-             $this->config['grant_types'])) {
+            if ( ! in_array($params['response_type'], $this->grant_types)) {
 
                 throw new OAuthServerClientException(
                     $this->errors['unsupported_grant_type'], 7);