diff --git a/CHANGELOG.md b/CHANGELOG.md
index 499183f..d484f2f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Changelog
 
+## [Unreleased]
+
+### Fixed
+
+- PHP `8.4` deprecation
+
 ## 4.1.0 - 2024-03-10
 
 ### Added
diff --git a/src/Main.php b/src/Main.php
index d43f03f..f9c9d08 100644
--- a/src/Main.php
+++ b/src/Main.php
@@ -22,7 +22,7 @@
 
 abstract class Main
 {
-    final public function __construct(Config $config = null)
+    final public function __construct(?Config $config = null)
     {
         $os = Factory::build($config);
         $makeRequest = ServerRequestFactory::default($os->clock());