diff --git a/src/BeSimple/SoapBundle/ServiceBinding/RpcLiteralResponseMessageBinder.php b/src/BeSimple/SoapBundle/ServiceBinding/RpcLiteralResponseMessageBinder.php
index ed7ecf8..b6b4361 100644
--- a/src/BeSimple/SoapBundle/ServiceBinding/RpcLiteralResponseMessageBinder.php
+++ b/src/BeSimple/SoapBundle/ServiceBinding/RpcLiteralResponseMessageBinder.php
@@ -85,7 +85,7 @@ class RpcLiteralResponseMessageBinder implements MessageBinderInterface
         $this->messageRefs[$hash] = $message;
 
         if (!$message instanceof $phpType) {
-            throw new \InvalidArgumentException(sprintf('The instance class must be "%s", "%s" given.', get_class($message), $phpType));
+            throw new \InvalidArgumentException(sprintf('The instance class must be "%s", "%s" given.', $phpType, get_class($message)));
         }
 
         $messageBinder = new MessageBinder($message);