diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 897b1c1..a8f9242 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -18,7 +18,6 @@ jobs:
           - '8.2'
           - '8.3'
         symfony-version:
-          - '5.4.*'
           - '6.3.*'
         coverage: [ 'none' ]
     steps:
diff --git a/Builder/EnvironmentBuilder.php b/Builder/EnvironmentBuilder.php
index bd50bac..25f943c 100644
--- a/Builder/EnvironmentBuilder.php
+++ b/Builder/EnvironmentBuilder.php
@@ -162,7 +162,7 @@ public function getPolicyRules(): SecurityPolicyRules
         return $this->rules;
     }
 
-    public function warmUp(string $cacheDir/* , ?string $buildDir = null */)/* : array */
+    public function warmUp(string $cacheDir, ?string $buildDir = null): array
     {
         $currentDir = $this->options['cache_dir'];
 
diff --git a/CacheWarmer/TwigSandboxCacheWarmer.php b/CacheWarmer/TwigSandboxCacheWarmer.php
index c01a18d..036b11e 100644
--- a/CacheWarmer/TwigSandboxCacheWarmer.php
+++ b/CacheWarmer/TwigSandboxCacheWarmer.php
@@ -14,7 +14,7 @@ public function __construct(EnvironmentBuilder $builder)
         $this->environmentBuilder = $builder;
     }
 
-    public function warmUp(string $cacheDir/* , ?string $buildDir = null */)/* : array */
+    public function warmUp(string $cacheDir, ?string $buildDir = null): array
     {
         return $this->environmentBuilder->warmUp($cacheDir);
     }
diff --git a/README.md b/README.md
index 8cb97ae..a37fc39 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@ There is [Twig](https://twig.symfony.com)-extension [Sandbox](https://twig.symfo
 
 ## Installation
 
-TwigSandboxBundle requires Symfony 5.4 or higher.
+TwigSandboxBundle requires Symfony 6.0 or higher.
 
 Install the bundle:
 
diff --git a/composer.json b/composer.json
index 485abd8..ac1731c 100644
--- a/composer.json
+++ b/composer.json
@@ -18,8 +18,8 @@
         "doctrine/annotations": "^1.13|^2.0",
         "php": "^8.1",
         "psr/cache": "~1.0|~2.0",
-        "symfony/framework-bundle": "^5.0|^6.0",
-        "symfony/validator": "^5.0|^6.0",
+        "symfony/framework-bundle": "^6.0",
+        "symfony/validator": "^6.0",
         "twig/twig": "^2.14 | ^3.0"
     },
     "autoload": {
@@ -32,22 +32,22 @@
         "phpstan/phpstan": "^1.0",
         "phpstan/phpstan-symfony": "^1.0",
         "phpunit/phpunit": "^8.5|^9.5",
-        "symfony/phpunit-bridge": "^5.0|^6.0",
-        "symfony/config": "^5.0|^6.0",
-        "symfony/dependency-injection": "^5.0|^6.0",
-        "symfony/event-dispatcher": "^5.0|^6.0",
-        "symfony/error-handler": "^5.0|^6.0",
-        "symfony/http-kernel": "^5.0|^6.0",
-        "symfony/http-foundation": "^5.0|^6.0",
-        "symfony/yaml": "^5.0|^6.0",
+        "symfony/phpunit-bridge": "^6.0",
+        "symfony/config": "^6.0",
+        "symfony/dependency-injection": "^6.0",
+        "symfony/event-dispatcher": "^6.0",
+        "symfony/error-handler": "^6.0",
+        "symfony/http-kernel": "^6.0",
+        "symfony/http-foundation": "^6.0",
+        "symfony/yaml": "^6.0",
         "symfony/deprecation-contracts": "^1.1|^2.0",
         "symfony/event-dispatcher-contracts": "^1.1|^2.0",
-        "symfony/routing": "^5.0|^6.0",
-        "symfony/finder": "^5.0|^6.0",
-        "symfony/filesystem": "^5.0|^6.0",
+        "symfony/routing": "^6.0",
+        "symfony/finder": "^6.0",
+        "symfony/filesystem": "^6.0",
         "symfony/translation-contracts": "^1.1|^2.0",
-        "symfony/var-exporter": "^5.0|^6.0",
-        "symfony/var-dumper": "^5.0|^6.0",
+        "symfony/var-exporter": "^6.0",
+        "symfony/var-dumper": "^6.0",
         "psr/log": "~1.0",
         "friendsofphp/php-cs-fixer": "^3"
     },