diff --git a/composer.json b/composer.json
index 1d4ad8d..d045720 100644
--- a/composer.json
+++ b/composer.json
@@ -30,18 +30,18 @@
         }
     },
     "require": {
-        "php": ">=7.1.3",
+        "php": ">=8.0",
         "mailjet/mailjet-apiv3-php": "^1.2",
         "mailjet/mailjet-swiftmailer": "^2.0",
-        "symfony/config": "^4.4|^5.0",
-        "symfony/console": "^4.4|^5.0",
-        "symfony/dependency-injection": "^4.4|^5.0",
-        "symfony/event-dispatcher": "^4.4|^5.0",
-        "symfony/framework-bundle": "^4.4|^5.0",
-        "symfony/http-foundation": "^4.4|^5.0",
-        "symfony/http-kernel": "^4.4|^5.0",
-        "symfony/routing": "^4.4|^5.0",
-        "symfony/yaml": "^4.4|^5.0"
+        "symfony/config": "^6|^5.0",
+        "symfony/console": "^6|^5.0",
+        "symfony/dependency-injection": "^6|^5.0",
+        "symfony/event-dispatcher": "^6|^5.0",
+        "symfony/framework-bundle": "^6|^5.0",
+        "symfony/http-foundation": "^6|^5.0",
+        "symfony/http-kernel": "^6|^5.0",
+        "symfony/routing": "^6|^5.0",
+        "symfony/yaml": "^6|^5.0"
     },
     "require-dev": {
         "phpspec/phpspec": "^5.1|^6.0|^7.0"
diff --git a/src/DependencyInjection/MailjetExtension.php b/src/DependencyInjection/MailjetExtension.php
index fadd801..ba1a9b3 100644
--- a/src/DependencyInjection/MailjetExtension.php
+++ b/src/DependencyInjection/MailjetExtension.php
@@ -54,7 +54,7 @@ public function load(array $configs, ContainerBuilder $container)
         $loader->load('services.yml');
     }
 
-    public function getAlias()
+    public function getAlias() : string
     {
         return 'mailjet';
     }
diff --git a/src/MailjetBundle.php b/src/MailjetBundle.php
index 45135fd..4f55c49 100644
--- a/src/MailjetBundle.php
+++ b/src/MailjetBundle.php
@@ -2,12 +2,13 @@
 
 namespace Mailjet\MailjetBundle;
 
+use Symfony\Component\DependencyInjection\Extension\ExtensionInterface;
 use Symfony\Component\HttpKernel\Bundle\Bundle;
 use Mailjet\MailjetBundle\DependencyInjection\MailjetExtension;
 
 class MailjetBundle extends Bundle
 {
-    public function getContainerExtension()
+    public function getContainerExtension(): ?ExtensionInterface
     {
         return new MailjetExtension();
     }