diff --git a/.github/workflows/pr_test.yml b/.github/workflows/pr_test.yml
index 9f66915..94c85e6 100644
--- a/.github/workflows/pr_test.yml
+++ b/.github/workflows/pr_test.yml
@@ -11,11 +11,11 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php: ["7.4", "8.0", "8.1", "8.2", "8.3"]
+        php: ["7.4", "8.0", "8.1", "8.2", "8.3", "8.4", "8.5"]
         composer-version: [prefer-lowest, prefer-stable]
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Install dependencies
         run: |
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 22f6fad..b273047 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # CHANGELOG
 
+## 4.2.0
+* Add support for PHP 8.4, 8.5
+* Implicitly nullable parameters (deprecated in PHP 8.4) are declared nullable
+
 ## 4.0.0
 
 - Add support for PHP 8.0, 8.1, 8.2
diff --git a/composer.json b/composer.json
index 738e18c..adc4f2b 100644
--- a/composer.json
+++ b/composer.json
@@ -19,7 +19,7 @@
     }
   ],
   "require": {
-    "php": ">=7.4 <8.4",
+    "php": ">=7.4 <8.6",
     "psr/log": "^1.0 || ^2.0 || ^3.0",
     "rexlabs/utility-belt": "^4.0",
     "guzzlehttp/guzzle": "^7.0",
diff --git a/src/Exceptions/ApiException.php b/src/Exceptions/ApiException.php
index b168501..317469e 100644
--- a/src/Exceptions/ApiException.php
+++ b/src/Exceptions/ApiException.php
@@ -28,7 +28,7 @@ class ApiException extends \RuntimeException
      * @param int             $code
      * @param \Throwable|null $previous
      */
-    public function __construct($message, $code = 0, \Throwable $previous = null)
+    public function __construct($message, $code = 0, ?\Throwable $previous = null)
     {
         parent::__construct($message, $code, $previous);
 
diff --git a/src/Hyper.php b/src/Hyper.php
index 972882e..18192fc 100644
--- a/src/Hyper.php
+++ b/src/Hyper.php
@@ -55,7 +55,7 @@ class Hyper
      *
      * @return Client
      */
-    public static function make(array $config = [], GuzzleClient $guzzle = null, LoggerInterface $logger = null): Client
+    public static function make(array $config = [], ?GuzzleClient $guzzle = null, ?LoggerInterface $logger = null): Client
     {
         $config = array_replace_recursive(self::$defaultConfig, $config);
         $guzzleConfig = $config['guzzle'] ?? [];
@@ -188,7 +188,7 @@ protected static function getBaseUri()
      *
      * @return Client
      */
-    public static function instance(array $config = [], GuzzleClient $guzzle = null, LoggerInterface $logger = null): Client
+    public static function instance(array $config = [], ?GuzzleClient $guzzle = null, ?LoggerInterface $logger = null): Client
     {
         if (!array_key_exists(static::class, self::$instances)) {
             static::$instances[static::class] = static::make($config, $guzzle, $logger);