diff --git a/src/Oauth2/Authentication/Server.php b/src/Oauth2/Authentication/Server.php
index 125cb93a..a7b1ac9a 100644
--- a/src/Oauth2/Authentication/Server.php
+++ b/src/Oauth2/Authentication/Server.php
@@ -410,7 +410,7 @@ class Server
 
         // The authorization code
         if ( ! isset($authParams['code']) && 
-            ! isset($_GET['code'])) {
+            ! isset($_POST['code'])) {
 
             throw new OAuthServerClientException(sprintf($this->errors['invalid_request'], 'code'), 0);