diff --git a/.github/workflows/cgl.yaml b/.github/workflows/cgl.yaml
index 67a80d3..d8be9d6 100644
--- a/.github/workflows/cgl.yaml
+++ b/.github/workflows/cgl.yaml
@@ -19,6 +19,7 @@ jobs:
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
+          # @todo Switch to PHP 8.4 once PHP-CS-Fixer supports it
           php-version: 8.3
           tools: composer:v2, composer-require-checker, composer-unused, cs2pr
           coverage: none
diff --git a/.github/workflows/tests.yaml b/.github/workflows/tests.yaml
index ead2af3..49bbec4 100644
--- a/.github/workflows/tests.yaml
+++ b/.github/workflows/tests.yaml
@@ -15,7 +15,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php-version: ["8.1", "8.2", "8.3"]
+        php-version: ["8.1", "8.2", "8.3", "8.4"]
         dependencies: ["highest", "lowest"]
     steps:
       - uses: actions/checkout@v4
@@ -52,7 +52,7 @@ jobs:
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
-          php-version: 8.3
+          php-version: 8.4
           tools: composer:v2
           coverage: pcov
 
diff --git a/composer.json b/composer.json
index 0b85cff..06948c1 100644
--- a/composer.json
+++ b/composer.json
@@ -12,7 +12,7 @@
 		}
 	],
 	"require": {
-		"php": "~8.1.0 || ~8.2.0 || ~8.3.0",
+		"php": "~8.1.0 || ~8.2.0 || ~8.3.0 || ~8.4.0",
 		"friendsofphp/php-cs-fixer": "^3.14"
 	},
 	"require-dev": {
diff --git a/composer.lock b/composer.lock
index fd99e58..9d2a3ba 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "f543375cb9455d43f30bf5f7e29a68a3",
+    "content-hash": "5b4c6d1445d8ca89a73971289d31c2ec",
     "packages": [
         {
             "name": "clue/ndjson-react",
@@ -5225,12 +5225,12 @@
     ],
     "aliases": [],
     "minimum-stability": "stable",
-    "stability-flags": {},
+    "stability-flags": [],
     "prefer-stable": false,
     "prefer-lowest": false,
     "platform": {
-        "php": "~8.1.0 || ~8.2.0 || ~8.3.0"
+        "php": "~8.1.0 || ~8.2.0 || ~8.3.0 || ~8.4.0"
     },
-    "platform-dev": {},
+    "platform-dev": [],
     "plugin-api-version": "2.6.0"
 }