diff --git a/.github/workflows/checks.yml b/.github/workflows/checks.yml
deleted file mode 100644
index 85e49bf..0000000
--- a/.github/workflows/checks.yml
+++ /dev/null
@@ -1,18 +0,0 @@
-name: Checks
-
-on:
-  push:
-    branches:
-      - master
-  pull_request:
-
-  roave-bc-check:
-    name: Roave BC Check
-    runs-on: ubuntu-latest
-
-    steps:
-      - name: Checkout code
-        uses: actions/checkout@v2
-
-      - name: Roave BC Check
-        uses: docker://nyholm/roave-bc-check-ga
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c4cef58..ad3f5c4 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -2,6 +2,8 @@ name: CI
 
 on:
   push:
+    branches:
+      - '*.x'
   pull_request:
 
 jobs:
@@ -10,11 +12,11 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        php: ['7.1', '7.2', '7.3', '7.4', '8.0']
+        php: ['7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2']
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
@@ -23,15 +25,8 @@ jobs:
           tools: composer:v2
           coverage: none
 
-      - name: Install PHP 7 dependencies
+      - name: Install dependencies
         run: composer update --prefer-dist --no-interaction --no-progress
-        if: "matrix.php != '8.0'"
-
-      - name: Install PHP 8 dependencies
-        run: |
-          composer require "phpdocumentor/reflection-docblock:^5.2@dev" --no-interaction --no-update
-          composer update --prefer-dist --prefer-stable --no-interaction --no-progress --ignore-platform-req=php
-        if: "matrix.php == '8.0'"
 
       - name: Execute tests
         run: composer test
@@ -41,11 +36,11 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        php: ['7.1', '7.2', '7.3', '7.4']
+        php: ['7.1', '7.4', '8.0', '8.1', '8.2']
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
@@ -68,7 +63,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
diff --git a/.github/workflows/static.yml b/.github/workflows/static.yml
index 8257a56..143e55e 100644
--- a/.github/workflows/static.yml
+++ b/.github/workflows/static.yml
@@ -3,17 +3,20 @@ name: Static analysis
 on:
   push:
     branches:
-      - master
+      - '*.x'
   pull_request:
 
 jobs:
   phpstan:
     name: PHPStan
     runs-on: ubuntu-latest
-    
+
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
+
+      - name: Remove phpspec
+        run: composer remove --dev friends-of-phpspec/phpspec-code-coverage phpspec/phpspec
 
       - name: PHPStan
         uses: docker://oskarstark/phpstan-ga
@@ -26,9 +29,9 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: PHP-CS-Fixer
         uses: docker://oskarstark/php-cs-fixer-ga
         with:
-          args: --dry-run --diff-format udiff
+          args: --dry-run
diff --git a/.gitignore b/.gitignore
index 1029e28..8bca981 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,5 @@
-.php_cs
-.php_cs.cache
+.php-cs-fixer.php
+.php-cs-fixer.cache
 /build/
 /composer.lock
 /phpspec.yml
diff --git a/.php-cs-fixer.dist.php b/.php-cs-fixer.dist.php
new file mode 100644
index 0000000..83809c2
--- /dev/null
+++ b/.php-cs-fixer.dist.php
@@ -0,0 +1,16 @@
+<?php
+
+$finder = PhpCsFixer\Finder::create()
+    ->in(__DIR__.'/src')
+    ->name('*.php')
+;
+
+$config = (new PhpCsFixer\Config())
+    ->setRiskyAllowed(true)
+    ->setRules([
+        '@Symfony' => true,
+    ])
+    ->setFinder($finder)
+;
+
+return $config;
diff --git a/.php_cs.dist b/.php_cs.dist
deleted file mode 100644
index 770eee4..0000000
--- a/.php_cs.dist
+++ /dev/null
@@ -1,16 +0,0 @@
-<?php
-
-$config = PhpCsFixer\Config::create()
-    ->setRiskyAllowed(true)
-    ->setRules([
-        '@Symfony' => true,
-        'array_syntax' => ['syntax' => 'short'],
-    ])
-    ->setFinder(
-        PhpCsFixer\Finder::create()
-            ->in(__DIR__.'/src')
-            ->name('*.php')
-    )
-;
-
-return $config;
diff --git a/.styleci.yml b/.styleci.yml
deleted file mode 100644
index 5328b61..0000000
--- a/.styleci.yml
+++ /dev/null
@@ -1,14 +0,0 @@
-preset: symfony
-
-finder:
-    exclude:
-        - "spec"
-    path:
-        - "src"
-        - "tests"
-
-enabled:
-    - short_array_syntax
-
-disabled:
-    - phpdoc_annotation_without_dot # This is still buggy: https://github.com/symfony/symfony/pull/19198
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 29b03e0..4c3d863 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,8 +6,23 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## [2.4.1] - 2024-09-23
 
-## [Unreleased]
+- Updated code to not raise warnings for nullable parameters in PHP 8.4.
+
+## [2.4.0] - 2023-04-14
+
+### Changed
+
+- Allow `psr/http-message` v2 in addition to v1
+- Deprecate `Http\Client\HttpClient`, use [PSR-18](https://www.php-fig.org/psr/psr-18/) instead
+
+## [2.3.0] - 2022-02-21
+
+### Changed
+
+- Enabled the `$onRejected` callback of `HttpRejectedPromise` to return a promise for implementing a retry
+  mechanism [#168](https://github.com/php-http/httplug/pull/168)
 
 ## [2.2.0] - 2020-07-13
 
diff --git a/README.md b/README.md
index aabcf25..a9b476a 100644
--- a/README.md
+++ b/README.md
@@ -2,12 +2,11 @@
 
 [![Latest Version](https://img.shields.io/github/release/php-http/httplug.svg?style=flat-square)](https://github.com/php-http/httplug/releases)
 [![Software License](https://img.shields.io/badge/license-MIT-brightgreen.svg?style=flat-square)](LICENSE)
-[![Build Status](https://img.shields.io/travis/php-http/httplug/master.svg?style=flat-square)](https://travis-ci.org/php-http/httplug)
+[![Build Status](https://github.com/php-http/httplug/actions/workflows/ci.yml/badge.svg)](https://github.com/php-http/httplug/actions/workflows/ci.yml)
 [![Code Coverage](https://img.shields.io/scrutinizer/coverage/g/php-http/httplug.svg?style=flat-square)](https://scrutinizer-ci.com/g/php-http/httplug)
 [![Quality Score](https://img.shields.io/scrutinizer/g/php-http/httplug.svg?style=flat-square)](https://scrutinizer-ci.com/g/php-http/httplug)
 [![Total Downloads](https://img.shields.io/packagist/dt/php-http/httplug.svg?style=flat-square)](https://packagist.org/packages/php-http/httplug)
 
-[![Slack Status](http://slack.httplug.io/badge.svg)](http://slack.httplug.io)
 [![Email](https://img.shields.io/badge/email-team@httplug.io-blue.svg?style=flat-square)](mailto:team@httplug.io)
 
 **HTTPlug, the HTTP client abstraction for PHP.**
@@ -16,19 +15,11 @@
 ## Intro
 
 HTTP client standard built on [PSR-7](http://www.php-fig.org/psr/psr-7/) HTTP
-messages. The HTTPlug client interface is compatible with the official standard
-for the HTTP client interface, [PSR-18](http://www.php-fig.org/psr/psr-18/).
-HTTPlug adds an interface for asynchronous HTTP requests, which PSR-18 does not
-cover.
-
-Since HTTPlug has already been widely adopted and a whole ecosystem has been
-built around it, we will keep maintaining this package for the time being.
-HTTPlug 2.0 and newer extend the PSR-18 interface to allow for a convenient
-migration path.
-
-New client implementations and consumers should use the PSR-18 interfaces
-directly. In the long term, we expect PSR-18 to completely replace the need
-for HTTPlug.
+messages. The HttpAsyncClient defines an asynchronous HTTP client for PHP.
+
+This package also provides a synchronous HttpClient interface with the same
+method signature as the [PSR-18](http://www.php-fig.org/psr/psr-18/) client.
+For synchronous requests, we recommend using PSR-18 directly.
 
 
 ## History
diff --git a/composer.json b/composer.json
index 268b27e..7391770 100644
--- a/composer.json
+++ b/composer.json
@@ -22,16 +22,11 @@
         "php": "^7.1 || ^8.0",
         "php-http/promise": "^1.1",
         "psr/http-client": "^1.0",
-        "psr/http-message": "^1.0"
+        "psr/http-message": "^1.0 || ^2.0"
     },
     "require-dev": {
-        "friends-of-phpspec/phpspec-code-coverage": "^4.1",
-        "phpspec/phpspec": "^5.1 || ^6.0"
-    },
-    "extra": {
-        "branch-alias": {
-            "dev-master": "2.x-dev"
-        }
+        "friends-of-phpspec/phpspec-code-coverage": "^4.1 || ^5.0 || ^6.0",
+        "phpspec/phpspec": "^5.1 || ^6.0 || ^7.0"
     },
     "autoload": {
         "psr-4": {
diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
index d45d0a4..c1629a6 100644
--- a/phpstan-baseline.neon
+++ b/phpstan-baseline.neon
@@ -1,7 +1,7 @@
 parameters:
 	ignoreErrors:
 		-
-			message: "#^Method Http\\\\Client\\\\Exception\\\\HttpException\\:\\:create\\(\\) has no return typehint specified\\.$#"
+			message: "#^Method Http\\\\Client\\\\Exception\\\\HttpException\\:\\:create\\(\\) has no return type specified\\.$#"
 			count: 1
 			path: src/Exception/HttpException.php
 
@@ -11,12 +11,11 @@ parameters:
 			path: src/Exception/HttpException.php
 
 		-
-			message: "#^Method Http\\\\Client\\\\Exception\\\\NetworkException\\:\\:setRequest\\(\\) has no return typehint specified\\.$#"
+			message: "#^Method Http\\\\Client\\\\Exception\\\\NetworkException\\:\\:setRequest\\(\\) has no return type specified\\.$#"
 			count: 1
 			path: src/Exception/NetworkException.php
 
 		-
-			message: "#^Method Http\\\\Client\\\\Exception\\\\RequestException\\:\\:setRequest\\(\\) has no return typehint specified\\.$#"
+			message: "#^Method Http\\\\Client\\\\Exception\\\\RequestException\\:\\:setRequest\\(\\) has no return type specified\\.$#"
 			count: 1
 			path: src/Exception/RequestException.php
-
diff --git a/spec/Exception/HttpExceptionSpec.php b/spec/Exception/HttpExceptionSpec.php
index 3658f56..20eb58e 100644
--- a/spec/Exception/HttpExceptionSpec.php
+++ b/spec/Exception/HttpExceptionSpec.php
@@ -10,6 +10,8 @@ class HttpExceptionSpec extends ObjectBehavior
 {
     function let(RequestInterface $request, ResponseInterface $response)
     {
+        $response->getStatusCode()->willReturn(500);
+
         $this->beConstructedWith('message', $request, $response);
     }
 
diff --git a/spec/Promise/HttpRejectedPromiseSpec.php b/spec/Promise/HttpRejectedPromiseSpec.php
index f46dcc5..5bc3f82 100644
--- a/spec/Promise/HttpRejectedPromiseSpec.php
+++ b/spec/Promise/HttpRejectedPromiseSpec.php
@@ -4,6 +4,7 @@
 
 use Http\Client\Exception;
 use Http\Client\Exception\TransferException;
+use Http\Client\Promise\HttpFulfilledPromise;
 use Http\Promise\Promise;
 use PhpSpec\ObjectBehavior;
 use Prophecy\Argument;
@@ -87,4 +88,19 @@ function it_throws_not_http_exception()
             throw new \Exception();
         });
     }
+
+    function it_returns_a_promise_when_rejected(ResponseInterface $response)
+    {
+        $exception = new TransferException();
+        $this->beConstructedWith($exception);
+
+        $promise = $this->then(null, function (Exception $exceptionReceived) use($exception, $response) {
+            return new HttpFulfilledPromise($response->getWrappedObject());
+        });
+
+        $promise->shouldHaveType('Http\Promise\Promise');
+        $promise->shouldHaveType('Http\Client\Promise\HttpFulfilledPromise');
+        $promise->getState()->shouldReturn(Promise::FULFILLED);
+        $promise->wait()->shouldReturnAnInstanceOf('Psr\Http\Message\ResponseInterface');
+    }
 }
diff --git a/src/Exception/HttpException.php b/src/Exception/HttpException.php
index 6c2a007..8af32f1 100644
--- a/src/Exception/HttpException.php
+++ b/src/Exception/HttpException.php
@@ -26,7 +26,7 @@ public function __construct(
         $message,
         RequestInterface $request,
         ResponseInterface $response,
-        \Exception $previous = null
+        ?\Exception $previous = null
     ) {
         parent::__construct($message, $request, $previous);
 
@@ -50,7 +50,7 @@ public function getResponse()
     public static function create(
         RequestInterface $request,
         ResponseInterface $response,
-        \Exception $previous = null
+        ?\Exception $previous = null
     ) {
         $message = sprintf(
             '[url] %s [http method] %s [status code] %s [reason phrase] %s',
diff --git a/src/Exception/NetworkException.php b/src/Exception/NetworkException.php
index 9b4f1e8..ce5f4d7 100644
--- a/src/Exception/NetworkException.php
+++ b/src/Exception/NetworkException.php
@@ -19,7 +19,7 @@ class NetworkException extends TransferException implements PsrNetworkException
     /**
      * @param string $message
      */
-    public function __construct($message, RequestInterface $request, \Exception $previous = null)
+    public function __construct($message, RequestInterface $request, ?\Exception $previous = null)
     {
         $this->setRequest($request);
 
diff --git a/src/Exception/RequestAwareTrait.php b/src/Exception/RequestAwareTrait.php
index 71b4bb8..f507982 100644
--- a/src/Exception/RequestAwareTrait.php
+++ b/src/Exception/RequestAwareTrait.php
@@ -16,9 +16,6 @@ private function setRequest(RequestInterface $request)
         $this->request = $request;
     }
 
-    /**
-     * {@inheritdoc}
-     */
     public function getRequest(): RequestInterface
     {
         return $this->request;
diff --git a/src/Exception/RequestException.php b/src/Exception/RequestException.php
index f6c60ce..dbed296 100644
--- a/src/Exception/RequestException.php
+++ b/src/Exception/RequestException.php
@@ -20,7 +20,7 @@ class RequestException extends TransferException implements PsrRequestException
     /**
      * @param string $message
      */
-    public function __construct($message, RequestInterface $request, \Exception $previous = null)
+    public function __construct($message, RequestInterface $request, ?\Exception $previous = null)
     {
         $this->setRequest($request);
 
diff --git a/src/HttpClient.php b/src/HttpClient.php
index 4442bd0..22b94aa 100644
--- a/src/HttpClient.php
+++ b/src/HttpClient.php
@@ -9,6 +9,8 @@
  *
  * Provide the Httplug HttpClient interface for BC.
  * You should typehint Psr\Http\Client\ClientInterface in new code
+ *
+ * @deprecated since version 2.4, use Psr\Http\Client\ClientInterface instead; see https://www.php-fig.org/psr/psr-18/
  */
 interface HttpClient extends ClientInterface
 {
diff --git a/src/Promise/HttpFulfilledPromise.php b/src/Promise/HttpFulfilledPromise.php
index 1ad32cd..ccdf48e 100644
--- a/src/Promise/HttpFulfilledPromise.php
+++ b/src/Promise/HttpFulfilledPromise.php
@@ -18,10 +18,7 @@ public function __construct(ResponseInterface $response)
         $this->response = $response;
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function then(callable $onFulfilled = null, callable $onRejected = null)
+    public function then(?callable $onFulfilled = null, ?callable $onRejected = null)
     {
         if (null === $onFulfilled) {
             return $this;
@@ -34,17 +31,11 @@ public function then(callable $onFulfilled = null, callable $onRejected = null)
         }
     }
 
-    /**
-     * {@inheritdoc}
-     */
     public function getState()
     {
         return Promise::FULFILLED;
     }
 
-    /**
-     * {@inheritdoc}
-     */
     public function wait($unwrap = true)
     {
         if ($unwrap) {
diff --git a/src/Promise/HttpRejectedPromise.php b/src/Promise/HttpRejectedPromise.php
index 8af97de..a489ad4 100644
--- a/src/Promise/HttpRejectedPromise.php
+++ b/src/Promise/HttpRejectedPromise.php
@@ -17,33 +17,29 @@ public function __construct(Exception $exception)
         $this->exception = $exception;
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function then(callable $onFulfilled = null, callable $onRejected = null)
+    public function then(?callable $onFulfilled = null, ?callable $onRejected = null)
     {
         if (null === $onRejected) {
             return $this;
         }
 
         try {
-            return new HttpFulfilledPromise($onRejected($this->exception));
+            $result = $onRejected($this->exception);
+            if ($result instanceof Promise) {
+                return $result;
+            }
+
+            return new HttpFulfilledPromise($result);
         } catch (Exception $e) {
             return new self($e);
         }
     }
 
-    /**
-     * {@inheritdoc}
-     */
     public function getState()
     {
         return Promise::REJECTED;
     }
 
-    /**
-     * {@inheritdoc}
-     */
     public function wait($unwrap = true)
     {
         if ($unwrap) {