diff --git a/src/MessageBird/Resources/Conversation/Conversations.php b/src/MessageBird/Resources/Conversation/Conversations.php
index 5fd10533..5d78dd1d 100644
--- a/src/MessageBird/Resources/Conversation/Conversations.php
+++ b/src/MessageBird/Resources/Conversation/Conversations.php
@@ -70,7 +70,7 @@ private function getStartUrl(): string
      * @throws Exceptions\RequestException
      * @throws Exceptions\ServerException
      */
-    public function create($object, array $query = null)
+    public function create($object, ?array $query = null)
     {
         $body = json_encode(['contactId' => $object], \JSON_THROW_ON_ERROR);