diff --git a/src/Consul.php b/src/Consul.php
index 0f1725fa..3f0aa212 100644
--- a/src/Consul.php
+++ b/src/Consul.php
@@ -154,7 +154,7 @@ class Consul
     public SessionClient $Session;
     public StatusClient $Status;
 
-    public function __construct(Config $config = null)
+    public function __construct(?Config $config = null)
     {
         $config = Config::merge($config);