diff --git a/src/Message/MessageFactory.php b/src/Message/MessageFactory.php
index a111d2f..1caadad 100644
--- a/src/Message/MessageFactory.php
+++ b/src/Message/MessageFactory.php
@@ -28,7 +28,7 @@ class MessageFactory implements MessageFactoryInterface
      *
      * @return RequestInterface
      */
-    public function createRequest($method, $uri, array $headers = [], array $options = [])
+    public function createRequest($method, $uri, array $headers = [], array $options = []): RequestInterface
     {
         $body = Json::encode($this->addIdToRequest($method, $options));