diff --git a/.envrc b/.envrc
index 1d953f4..1b5ce28 100644
--- a/.envrc
+++ b/.envrc
@@ -1 +1,2 @@
 use nix
+watch_file flake.nix flake.lock
diff --git a/.github/workflows/main.yaml b/.github/workflows/main.yaml
index 5279933..3f37c41 100644
--- a/.github/workflows/main.yaml
+++ b/.github/workflows/main.yaml
@@ -10,16 +10,16 @@ env:
 
 jobs:
   tests:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     strategy:
       matrix:
         php:
+          - '8.4'
+          - '8.3'
           - '8.2'
           - '8.1'
           - '8.0'
           - '7.4'
-          - '7.3'
-          - '7.2'
         include:
           - php: '7.4'
             cs_fixer: true
@@ -27,13 +27,13 @@ jobs:
             phpstan: true
     name: 'Check with PHP ${{ matrix.php }}'
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Install Nix
-        uses: cachix/install-nix-action@v20
+        uses: cachix/install-nix-action@v31
 
       - name: Set up Nix cache
-        uses: cachix/cachix-action@v12
+        uses: cachix/cachix-action@v16
         with:
           # Use cache from https://github.com/fossar/nix-phps
           name: fossar
@@ -46,7 +46,7 @@ jobs:
         run: |
           echo "dir=$(composer config cache-files-dir)" >> "$GITHUB_OUTPUT"
 
-      - uses: actions/cache@v3
+      - uses: actions/cache@v4
         with:
           path: ${{ steps.composer-cache.outputs.dir }}
           key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
diff --git a/.gitignore b/.gitignore
index 57872d0..08b8e95 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,5 @@
 /vendor/
+.direnv/
+.php-cs-fixer.cache
+.phpunit.result.cache
+phpstan.neon
diff --git a/.php-cs-fixer.php b/.php-cs-fixer.php
index 67ba003..5c1fa19 100644
--- a/.php-cs-fixer.php
+++ b/.php-cs-fixer.php
@@ -6,15 +6,22 @@
 $rules = [
     '@Symfony' => true,
     '@Symfony:risky' => true,
-    '@PHP71Migration' => true,
-    '@PHP71Migration:risky' => true,
+    '@PHP74Migration' => true,
+    '@PHP74Migration:risky' => true,
+    'phpdoc_to_property_type' => true,
     // 'phpdoc_to_param_type' => true,
-    'phpdoc_to_return_type' => true,
+    // 'phpdoc_to_return_type' => true,
     'phpdoc_types_order' => false,
 
     // overwrite some Symfony rules
-    'braces' => ['position_after_functions_and_oop_constructs' => 'same'],
-    'function_declaration' => ['closure_function_spacing' => 'none'],
+    'braces_position' => [
+        'functions_opening_brace' => 'same_line',
+        'classes_opening_brace' => 'same_line',
+    ],
+    'function_declaration' => [
+        'closure_function_spacing' => 'none',
+        'closure_fn_spacing' => 'none',
+    ],
     'concat_space' => ['spacing' => 'one'],
     'phpdoc_align' => false,
     'yoda_style' => false,
diff --git a/NEWS.md b/NEWS.md
index 1598c41..f1427c5 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,8 @@
 # guzzle-transcoder changes
 
+## 0.3.1 – 2025-03-15
+- Raise minimum PHP version to 7.4.0.
+
 ## 0.3.0 – 2023-03-06
 - Raise minimum PHP version to 7.2.5.
 - Add support for fossar/transcoder 2.0.
diff --git a/composer.json b/composer.json
index aad6654..6e8ab3e 100644
--- a/composer.json
+++ b/composer.json
@@ -3,15 +3,16 @@
     "description": "Guzzle plugin that converts responses to UTF-8",
     "type": "library",
     "require": {
-        "php": ">=7.2.5",
+        "php": ">=7.4.0",
         "guzzlehttp/guzzle": "^6.3 || ^7.0",
-        "fossar/transcoder": "^1.0 || ^2.0",
+        "fossar/transcoder": "^1.0 || ^2.0 || ^3.0",
         "guzzlehttp/psr7": "^1.7 || ^2.0"
     },
     "require-dev" : {
         "friendsofphp/php-cs-fixer": "^3.0",
         "php-parallel-lint/php-parallel-lint": "^1.0",
-        "symfony/phpunit-bridge": "^6.2"
+        "symfony/phpunit-bridge": "^6.2 || ^7.0",
+        "phpstan/phpstan": "^2.1"
     },
     "autoload": {
         "psr-4": { "Fossar\\GuzzleTranscoder\\": "src/" }
@@ -28,7 +29,7 @@
     ],
     "config": {
         "platform": {
-            "php": "7.2.5"
+            "php": "7.4.0"
         }
     },
     "scripts": {
diff --git a/flake.lock b/flake.lock
index 6b23d4c..ed532a6 100644
--- a/flake.lock
+++ b/flake.lock
@@ -3,11 +3,11 @@
     "flake-compat": {
       "flake": false,
       "locked": {
-        "lastModified": 1673956053,
-        "narHash": "sha256-4gtG9iQuiKITOjNQQeQIpoIB6b16fm+504Ch3sNKLd8=",
+        "lastModified": 1733328505,
+        "narHash": "sha256-NeCCThCEP3eCl2l/+27kNNK7QrwZB1IJCrXfrbv5oqU=",
         "owner": "edolstra",
         "repo": "flake-compat",
-        "rev": "35bb57c0c8d8b62bbfd284272c928ceb64ddbde9",
+        "rev": "ff81ac966bb2cae68946d5ed5fc4994f96d0ffec",
         "type": "github"
       },
       "original": {
@@ -18,11 +18,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1677852945,
-        "narHash": "sha256-liiVJjkBTuBTAkRW3hrI8MbPD2ImYzwUpa7kvteiKhM=",
+        "lastModified": 1741310760,
+        "narHash": "sha256-aizILFrPgq/W53Jw8i0a1h1GZAAKtlYOrG/A5r46gVM=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "f5ffd5787786dde3a8bf648c7a1b5f78c4e01abb",
+        "rev": "de0fe301211c267807afd11b12613f5511ff7433",
         "type": "github"
       },
       "original": {
@@ -39,11 +39,11 @@
         "utils": "utils"
       },
       "locked": {
-        "lastModified": 1678028979,
-        "narHash": "sha256-qFSN1sKlavyqUl9Vz60+iniYbTLfXtdAwFmTDdlLN5o=",
+        "lastModified": 1741586946,
+        "narHash": "sha256-EI5TFGNt2ObkK8MdBASS9LVkWT0qTqOljFFP2+RjZI0=",
         "owner": "fossar",
         "repo": "nix-phps",
-        "rev": "181dee32f3d47312674462cff30fcca661c6c643",
+        "rev": "e48727edd2dbbbd7b9181bd284569554f6e4e5a6",
         "type": "github"
       },
       "original": {
@@ -57,13 +57,31 @@
         "phps": "phps"
       }
     },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    },
     "utils": {
+      "inputs": {
+        "systems": "systems"
+      },
       "locked": {
-        "lastModified": 1676283394,
-        "narHash": "sha256-XX2f9c3iySLCw54rJ/CZs+ZK6IQy7GXNY4nSOyu2QG4=",
+        "lastModified": 1731533236,
+        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
         "owner": "numtide",
         "repo": "flake-utils",
-        "rev": "3db36a8b464d0c4532ba1c7dda728f4576d6d073",
+        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
         "type": "github"
       },
       "original": {
diff --git a/flake.nix b/flake.nix
index 40ad678..2907829 100644
--- a/flake.nix
+++ b/flake.nix
@@ -34,7 +34,7 @@
             # Composer and PHP.
             php
             php.packages.composer
-            php.packages.phpstan
+            pkgs.phpactor
           ];
         };
       };
diff --git a/phpstan.neon b/phpstan.dist.neon
similarity index 100%
rename from phpstan.neon
rename to phpstan.dist.neon
diff --git a/src/GuzzleTranscoder.php b/src/GuzzleTranscoder.php
index a07bb05..3786f60 100644
--- a/src/GuzzleTranscoder.php
+++ b/src/GuzzleTranscoder.php
@@ -12,17 +12,13 @@
 use Psr\Http\Message\ResponseInterface;
 
 class GuzzleTranscoder {
-    /** @var ?TranscoderInterface */
-    private $transcoder;
+    private ?TranscoderInterface $transcoder;
 
-    /** @var string */
-    private $targetEncoding;
+    private string $targetEncoding;
 
-    /** @var bool */
-    private $replaceHeaders;
+    private bool $replaceHeaders;
 
-    /** @var bool */
-    private $replaceContent;
+    private bool $replaceContent;
 
     /**
      * Constructs a class for transcoding Responses.
@@ -56,7 +52,7 @@ private function createTranscoder(): TranscoderInterface {
     public function convert(ResponseInterface $response): ResponseInterface {
         $stream = $response->getBody();
 
-        /** @var array<string, string[]> */
+        /** @var array<string, list<string>> */
         $headers = $response->getHeaders();
         $result = $this->convertResponse($headers, (string) $stream);
         if ($result !== null) {
@@ -81,11 +77,10 @@ public function convert(ResponseInterface $response): ResponseInterface {
      */
     public function __invoke(callable $handler): callable {
         return function(RequestInterface $request, array $options) use ($handler): PromiseInterface {
+            /** @var array<string, mixed> $options */
             $promise = $handler($request, $options);
 
-            return $promise->then(function(ResponseInterface $response): ResponseInterface {
-                return $this->convert($response);
-            });
+            return $promise->then(fn(ResponseInterface $response): ResponseInterface => $this->convert($response));
         };
     }
 
@@ -100,9 +95,9 @@ public function __invoke(callable $handler): callable {
      *
      * Otherwise an array containing the new headers and content is returned.
      *
-     * @param array<string, string[]> $headers
+     * @param array<string, list<string>> $headers
      *
-     * @return ?array{headers: array<string, string[]>, content: string}
+     * @return ?array{headers: array<string, list<string>>, content: string}
      */
     public function convertResponse(array $headers, string $content): ?array {
         $headerDeclaredEncoding = null;
diff --git a/src/Utils.php b/src/Utils.php
index b808994..70f9199 100644
--- a/src/Utils.php
+++ b/src/Utils.php
@@ -72,7 +72,7 @@ class Utils {
      *    [Basic=>null, realm=>'"foo\bar"']
      *    ["</TheBook/chapter,2>" => null, "rel" => "pre,vious", "title*" => "UTF-8'de'letztes%20Kapitel" ], ["</TheBook/chapter4>" => null, "rel" => "next", "title*" => "UTF-8'de'n%c3%a4chstes%20Kapitel" ]
      *
-     * @param string[]|string $headerValues
+     * @param list<string>|string $headerValues
      *
      * @throws \Exception
      *
@@ -174,7 +174,7 @@ public static function joinHttpHeaderWords(array $headerValues): string {
         }
         /** @var array<array<string, ?string>> $headerValues */
         $spaces = '\\s';
-        $ctls = '\\x00-\\x1F\\x7F'; //@see http://stackoverflow.com/a/1497928/413531
+        $ctls = '\\x00-\\x1F\\x7F'; // @see http://stackoverflow.com/a/1497928/413531
         $tspecials = '()<>@,;:<>/[\\]?.="\\\\';
         $tokenPattern = "#^[^{$spaces}{$ctls}{$tspecials}]+$#";
         $result = [];
diff --git a/tests/ContentTypeExtractorTest.php b/tests/ContentTypeExtractorTest.php
index 0de2e9e..c2bee1d 100644
--- a/tests/ContentTypeExtractorTest.php
+++ b/tests/ContentTypeExtractorTest.php
@@ -27,8 +27,7 @@ public function contentTypes(): iterable {
         yield 'HTML5, double quotes' => [
             <<<HTML
                 <meta charset="iso-8859-1">
-HTML
-            ,
+                HTML,
             'iso-8859-1',
             [
                 '<meta charset="iso-8859-1">' => '<meta charset="placeholder-encoding">',
@@ -38,8 +37,7 @@ public function contentTypes(): iterable {
         yield 'HTML5, single quotes' => [
             <<<HTML
                 <meta charset='iso-8859-1'>
-HTML
-            ,
+                HTML,
             'iso-8859-1',
             [
                 "<meta charset='iso-8859-1'>" => "<meta charset='placeholder-encoding'>",
@@ -49,8 +47,7 @@ public function contentTypes(): iterable {
         yield 'HTML5, unquoted' => [
             <<<HTML
                 <meta charset=iso-8859-1>
-HTML
-            ,
+                HTML,
             'iso-8859-1',
             [
                 '<meta charset=iso-8859-1>' => '<meta charset=placeholder-encoding>',
@@ -60,8 +57,7 @@ public function contentTypes(): iterable {
         yield 'HTML5, unquoted, spaces around' => [
             <<<HTML
                 <meta charset = iso-8859-1>
-HTML
-            ,
+                HTML,
             'iso-8859-1',
             [
                 '<meta charset = iso-8859-1>' => '<meta charset=placeholder-encoding>',
@@ -71,8 +67,7 @@ public function contentTypes(): iterable {
         yield 'HTML5, unquoted, extra attributes' => [
             <<<HTML
                 <meta foo charset=iso-8859-1 bar baz="2">
-HTML
-            ,
+                HTML,
             'iso-8859-1',
             [
                 '<meta foo charset=iso-8859-1 bar baz="2">' => '<meta foo charset=placeholder-encoding bar baz="2">',
@@ -82,8 +77,7 @@ public function contentTypes(): iterable {
         yield 'HTML5, random case' => [
             <<<HTML
                 <MeTA chArSEt="ISo-8859-1">
-HTML
-            ,
+                HTML,
             'ISo-8859-1',
             [
                 '<MeTA chArSEt="ISo-8859-1">' => '<MeTA charset="placeholder-encoding">',
@@ -93,8 +87,7 @@ public function contentTypes(): iterable {
         yield '(X)HTML5, unquoted' => [
             <<<HTML
                 <meta charset=iso-8859-1 />
-HTML
-            ,
+                HTML,
             'iso-8859-1',
             [
                 '<meta charset=iso-8859-1 />' => '<meta charset=placeholder-encoding />',
@@ -104,8 +97,7 @@ public function contentTypes(): iterable {
         yield '(X)HTML5, tight' => [
             <<<HTML
                 <meta charset="iso-8859-1"/>
-HTML
-            ,
+                HTML,
             'iso-8859-1',
             [
                 '<meta charset="iso-8859-1"/>' => '<meta charset="placeholder-encoding"/>',
@@ -117,8 +109,7 @@ public function contentTypes(): iterable {
         yield '(X)HTML5, unquoted, misplaced solidus' => [
             <<<HTML
                 <meta charset=iso-8859-1/>
-HTML
-            ,
+                HTML,
             'iso-8859-1/',
             [
                 '<meta charset=iso-8859-1/>' => '<meta charset=placeholder-encoding>',
@@ -127,9 +118,8 @@ public function contentTypes(): iterable {
 
         yield 'HTML4, double quotes' => [
             <<<HTML
-                 <meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">
-HTML
-            ,
+                <meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">
+                HTML,
             'ISO-8859-1',
             [
                 '<meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">' => '<meta http-equiv="content-type" content="text/html; charset=placeholder-encoding">',
@@ -138,9 +128,8 @@ public function contentTypes(): iterable {
 
         yield 'HTML4, double quotes, other way around' => [
             <<<HTML
-                 <meta content="text/html; charset=ISO-8859-1" http-equiv="content-type">
-HTML
-            ,
+                <meta content="text/html; charset=ISO-8859-1" http-equiv="content-type">
+                HTML,
             'ISO-8859-1',
             [
                 '<meta content="text/html; charset=ISO-8859-1" http-equiv="content-type">' => '<meta content="text/html; charset=placeholder-encoding" http-equiv="content-type">',
@@ -149,9 +138,8 @@ public function contentTypes(): iterable {
 
         yield 'HTML4, double quotes, extra attributes, other way around' => [
             <<<HTML
-                 <meta foo="bar" content="text/html; charset=ISO-8859-1" test middle http-equiv="content-type" after='something'>
-HTML
-            ,
+                <meta foo="bar" content="text/html; charset=ISO-8859-1" test middle http-equiv="content-type" after='something'>
+                HTML,
             'ISO-8859-1',
             [
                 '<meta foo="bar" content="text/html; charset=ISO-8859-1" test middle http-equiv="content-type" after=\'something\'>' => '<meta foo="bar" content="text/html; charset=placeholder-encoding" test middle http-equiv="content-type" after=\'something\'>',
@@ -160,9 +148,8 @@ public function contentTypes(): iterable {
 
         yield 'HTML4, single quotes' => [
             <<<HTML
-                 <meta http-equiv='content-type' content='text/html; charset=ISO-8859-1'>
-HTML
-            ,
+                <meta http-equiv='content-type' content='text/html; charset=ISO-8859-1'>
+                HTML,
             'ISO-8859-1',
             [
                 "<meta http-equiv='content-type' content='text/html; charset=ISO-8859-1'>" => "<meta http-equiv='content-type' content='text/html; charset=placeholder-encoding'>",
@@ -171,9 +158,8 @@ public function contentTypes(): iterable {
 
         yield 'HTML4, unquoted+single quotes' => [
             <<<HTML
-                 <meta http-equiv=content-type content='text/html; charset=ISO-8859-1'>
-HTML
-            ,
+                <meta http-equiv=content-type content='text/html; charset=ISO-8859-1'>
+                HTML,
             'ISO-8859-1',
             [
                 "<meta http-equiv=content-type content='text/html; charset=ISO-8859-1'>" => "<meta http-equiv=content-type content='text/html; charset=placeholder-encoding'>",
@@ -183,9 +169,8 @@ public function contentTypes(): iterable {
         // https://httpwg.org/specs/rfc9110.html#field.content-type
         yield 'HTML4, internally quoted, extra parameters' => [
             <<<HTML
-                 <meta http-equiv=content-type content='text/html;foo;charset="ISO-8859-1";bar'>
-HTML
-            ,
+                <meta http-equiv=content-type content='text/html;foo;charset="ISO-8859-1";bar'>
+                HTML,
             'ISO-8859-1',
             [
                 "<meta http-equiv=content-type content='text/html;foo;charset=\"ISO-8859-1\";bar'>" => "<meta http-equiv=content-type content='text/html; foo; charset=placeholder-encoding; bar'>",
@@ -194,9 +179,8 @@ public function contentTypes(): iterable {
 
         yield 'HTML4, single quotes+double quotes+spaces around' => [
             <<<HTML
-                 <meta http-equiv =  "content-type" content  	=  "text/html; charset=ISO-8859-1">
-HTML
-            ,
+                <meta http-equiv =  "content-type" content  	=  "text/html; charset=ISO-8859-1">
+                HTML,
             'ISO-8859-1',
             [
                 '<meta http-equiv =  "content-type" content  	=  "text/html; charset=ISO-8859-1">' => '<meta http-equiv =  "content-type" content="text/html; charset=placeholder-encoding">',
@@ -205,9 +189,8 @@ public function contentTypes(): iterable {
 
         yield 'HTML4, random case' => [
             <<<HTML
-                 <meTA HTTp-EQuIv="conTeNt-TYpe" CoNTeNt="text/Html; cHArSeT=ISO-8859-1">
-HTML
-            ,
+                <meTA HTTp-EQuIv="conTeNt-TYpe" CoNTeNt="text/Html; cHArSeT=ISO-8859-1">
+                HTML,
             'ISO-8859-1',
             [
                 '<meTA HTTp-EQuIv="conTeNt-TYpe" CoNTeNt="text/Html; cHArSeT=ISO-8859-1">' => '<meTA HTTp-EQuIv="conTeNt-TYpe" content="text/Html; cHArSeT=placeholder-encoding">',
@@ -216,9 +199,8 @@ public function contentTypes(): iterable {
 
         yield '(X)HTML4' => [
             <<<HTML
-                 <meta http-equiv="content-type" content="text/html; charset=ISO-8859-1"/>
-HTML
-            ,
+                <meta http-equiv="content-type" content="text/html; charset=ISO-8859-1"/>
+                HTML,
             'ISO-8859-1',
             [
                 '<meta http-equiv="content-type" content="text/html; charset=ISO-8859-1"/>' => '<meta http-equiv="content-type" content="text/html; charset=placeholder-encoding"/>',
@@ -227,11 +209,10 @@ public function contentTypes(): iterable {
 
         yield 'multiple declarations' => [
             <<<HTML
-                 <meta http-equiv="content-type" test content="text/html; charset=ISO-8859-1">
-                 <meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">
-                 <meta charset=UTF-8>
-HTML
-            ,
+                <meta http-equiv="content-type" test content="text/html; charset=ISO-8859-1">
+                <meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">
+                <meta charset=UTF-8>
+                HTML,
             'ISO-8859-1',
             [
                 '<meta http-equiv="content-type" test content="text/html; charset=ISO-8859-1">' => '<meta http-equiv="content-type" test content="text/html; charset=placeholder-encoding">',
diff --git a/tests/GuzzleTranscoderTest.php b/tests/GuzzleTranscoderTest.php
index cceb8c7..fac9e20 100644
--- a/tests/GuzzleTranscoderTest.php
+++ b/tests/GuzzleTranscoderTest.php
@@ -214,7 +214,7 @@ public function testConvertResponse(): void {
      * Gets the headers from a HTTP response as one dimensional associative array
      * with header names as keys. The header values will not be parsed but saved as-is!
      *
-     * @return array{headers: array<string, string[]>, body: string}
+     * @return array{headers: array<string, list<string>>, body: string}
      */
     private function splitHeadersAndContentFromHttpResponseString(string $responseString): array {
         $lines = explode("\n", $responseString);
diff --git a/tests/ReadmeTest.php b/tests/ReadmeTest.php
index 1ebcd7c..2bfb0e6 100644
--- a/tests/ReadmeTest.php
+++ b/tests/ReadmeTest.php
@@ -36,8 +36,8 @@ public function readmeExamples(): iterable {
         foreach ($matches as $match) {
             $mockedSourceBody = file_get_contents(__DIR__ . '/resources/' . $match['response']);
             \assert($mockedSourceBody !== false); // For PHPStan.
+            /** @var array<string, string> $mockedHeaders */
             $mockedHeaders = json_decode($match['headers'], true);
-            \assert(\is_array($mockedHeaders)); // For PHPStan.
             $expectedBody = file_get_contents(__DIR__ . '/resources/' . $match['expected']);
             \assert($expectedBody !== false); // For PHPStan.