diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index b850e33..f9e740d 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -1,61 +1,44 @@
 name: Run tests
+
 on:
   push:
     branches:
-    # Only mainline branches, features etc are covered on the pull_request trigger
-    - '*.x'
+      # Only mainline branches, features etc are covered on the pull_request trigger
+      - '*.x'
   pull_request:
 
 jobs:
+
   run-tests:
-    runs-on: ubuntu-latest
     name: Run tests
+    runs-on: ubuntu-latest
+
     strategy:
       fail-fast: false
       matrix:
-        php_version:
-        - '8.1'
-        - '8.2'
-        - '8.3'
-        dependencies:
-        - 'default'
-        include:
-        - php_version: '8.1'
-          dependencies: 'lowest'
-        - php_version: '8.2'
-          dependencies: 'lowest'
-        - php_version: '8.3'
-          dependencies: 'lowest'
+        php-version:
+          - '8.1'
+          - '8.2'
+          - '8.3'
+          - '8.4'
+        dependency-versions:
+          - 'lowest'
+          - 'default'
+
     steps:
-    - name: Setup PHP
-      uses: shivammathur/setup-php@v2
-      with:
-        php-version: ${{ matrix.php_version }}
-        tools: composer:v2
-
-    - name: Checkout
-      uses: actions/checkout@v2
-
-    - name: Get Composer Cache Directory
-      id: composer-cache
-      run: |
-        echo "::set-output name=dir::$(composer config cache-files-dir)"
-    - uses: actions/cache@v2
-      with:
-        path: ${{ steps.composer-cache.outputs.dir }}
-        key: ${{ runner.os }}-composer-${{ matrix.dependencies }}-${{ hashFiles('**/composer.lock') }}
-        restore-keys: |
-          ${{ runner.os }}-composer-${{ matrix.dependencies }}
-    - name: Install composer dependencies
-      env:
-        DEPENDENCIES: ${{ matrix.dependencies }}
-      run: |
-        if [ $DEPENDENCIES == 'lowest' ]
-        then
-          composer update --prefer-lowest --no-interaction --no-progress
-        else
-          composer install --no-interaction --no-progress
-        fi
-    - name: Run unit tests
-      run: |
-        vendor/bin/phpunit
\ No newline at end of file
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php-version }}
+          tools: composer:v2
+
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install composer dependencies
+        uses: ramsey/composer-install@v3
+        with:
+          dependency-versions: ${{ matrix.dependency-versions }}
+
+      - name: Run PHPUnit
+        run: vendor/bin/phpunit
\ No newline at end of file
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 920f23b..f36a8e4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 ### Unreleased
 
+### v2.4.0 (2025-05-27)
+
+* Support PHP 8.4
+
 ### v2.3.0 (2024-11-28)
 
 * Add support for venue search endpoint
diff --git a/composer.json b/composer.json
index c6c10cc..31b1b07 100644
--- a/composer.json
+++ b/composer.json
@@ -11,12 +11,13 @@
     }
   ],
   "require": {
-    "guzzlehttp/guzzle": "^7.0",
-    "php": "~8.1.0 || ~8.2.0 || ~8.3.0"
+    "guzzlehttp/guzzle": "^7.9.2",
+    "php": "~8.1.0 || ~8.2.0 || ~8.3.0 || ~8.4.0"
   },
   "require-dev": {
-    "phpunit/phpunit": "^10.5",
-    "ergebnis/phpunit-slow-test-detector": "^2.15"
+    "guzzlehttp/promises": ">=2.0.4",
+    "phpunit/phpunit": "^10.5.45",
+    "ergebnis/phpunit-slow-test-detector": "^2.19.1"
   },
   "support": {
     "source": "https://github.com/festivalslab/api-client-php",
diff --git a/src/FestivalsApiClient.php b/src/FestivalsApiClient.php
index c288620..8bacbdc 100644
--- a/src/FestivalsApiClient.php
+++ b/src/FestivalsApiClient.php
@@ -15,6 +15,7 @@
 use GuzzleHttp\Exception\BadResponseException;
 use GuzzleHttp\Exception\GuzzleException;
 use GuzzleHttp\Psr7\Request;
+use GuzzleHttp\Utils;
 use InvalidArgumentException;
 use Psr\Http\Message\ResponseInterface;
 use function http_build_query;
@@ -123,7 +124,7 @@ protected function createRequest(string $url): Request
     protected function decodeJsonResponse(ResponseInterface $response): array
     {
         try {
-            return \GuzzleHttp\json_decode((string) $response->getBody(), TRUE);
+            return Utils::jsonDecode((string) $response->getBody(), TRUE);
         } catch (InvalidArgumentException $e) {
             throw FestivalsApiClientException::invalidJsonResponse($response->getStatusCode(), $e);
         }
@@ -160,7 +161,7 @@ protected function handleApiError(BadResponseException $e): void
         $url  = (string) $e->getRequest()->getUri();
 
         try {
-            $decoded = \GuzzleHttp\json_decode($e->getResponse()->getBody(), TRUE);
+            $decoded = Utils::jsonDecode($e->getResponse()->getBody(), TRUE);
             if (isset($decoded['error'])) {
                 $msg = $decoded['error'];
             }