diff --git a/src/Message.php b/src/Message.php
index 077c498f8..71cbc1d39 100644
--- a/src/Message.php
+++ b/src/Message.php
@@ -89,7 +89,10 @@ public function getContent()
     {
         return $this->content;
     }
-    
+
+    /**
+     * @return string
+     */
     public function toString()
     {
         $request = '';