diff --git a/composer.json b/composer.json
index bd97aec..c244510 100644
--- a/composer.json
+++ b/composer.json
@@ -5,7 +5,7 @@
     "license": "Apache-2.0",
     "require": {
         "php": ">=8.1",
-        "ccmbenchmark/ting": "^3.11",
+        "ccmbenchmark/ting": "^3.11 || ^4.0",
         "doctrine/cache": "^1.10",
         "symfony/validator": "^4.4 || ^5.0 || ^6.0 || ^7.0",
         "symfony/http-kernel": "^4.4 || ^5.0 || ^6.0 || ^7.0",
diff --git a/src/TingBundle/Serializer/SymfonySerializer.php b/src/TingBundle/Serializer/SymfonySerializer.php
index cc3fdb8..6b9dd6d 100644
--- a/src/TingBundle/Serializer/SymfonySerializer.php
+++ b/src/TingBundle/Serializer/SymfonySerializer.php
@@ -8,13 +8,13 @@ class SymfonySerializer implements SerializerInterface
 {
     public function __construct(private readonly ?\Symfony\Component\Serializer\SerializerInterface $serializer = null) {}
 
-    public function serialize($toSerialize, array $options = [])
+    public function serialize($toSerialize, array $options = []): mixed
     {
         $this->throwOnNullSerializer();
         return $this->serializer->serialize($toSerialize, 'json', $options['context'] ?? []);
     }
 
-    public function unserialize($serialized, array $options = [])
+    public function unserialize($serialized, array $options = []): mixed
     {
         if ($serialized === null) {
             return null;
@@ -32,4 +32,4 @@ private function throwOnNullSerializer()
             throw new \RuntimeException('SymfonySerializer requires symfony/serializer to be installed. Use composer require symfony/serializer to add it.');
         }
     }
-}
\ No newline at end of file
+}