diff --git a/composer.json b/composer.json
index 9c2f076..5d4082b 100644
--- a/composer.json
+++ b/composer.json
@@ -28,7 +28,7 @@
     "require": {
         "php": ">=8.1",
         "react/event-loop": "^1.2",
-        "react/promise": "^3.0 || ^2.8 || ^1.2.1"
+        "react/promise": "^3.2 || ^2.8 || ^1.2.1"
     },
     "require-dev": {
         "phpstan/phpstan": "1.10.39",
diff --git a/src/FiberFactory.php b/src/FiberFactory.php
index 93480e6..ee90818 100644
--- a/src/FiberFactory.php
+++ b/src/FiberFactory.php
@@ -22,7 +22,7 @@ public static function create(): FiberInterface
         return (self::factory())();
     }
 
-    public static function factory(\Closure $factory = null): \Closure
+    public static function factory(?\Closure $factory = null): \Closure
     {
         if ($factory !== null) {
             self::$factory = $factory;