diff --git a/src/League/OAuth2/Server/Grant/AuthCode.php b/src/League/OAuth2/Server/Grant/AuthCode.php
index b33bd6dd6..f0d9dbed4 100644
--- a/src/League/OAuth2/Server/Grant/AuthCode.php
+++ b/src/League/OAuth2/Server/Grant/AuthCode.php
@@ -108,7 +108,7 @@ public function checkAuthoriseParams($inputParams = array())
         }
 
         // Validate scopes
-        $scopes = explode($this->authServer->getScopeDelimeter(), $authParams['scope']);
+        $scopes = explode((string)$this->authServer->getScopeDelimeter(), $authParams['scope']);
 
         for ($i = 0; $i < count($scopes); $i++) {
             $scopes[$i] = trim($scopes[$i]);