diff --git a/.github/workflows/codecov.yml b/.github/workflows/codecov.yml
index 190b4da..7ad749b 100644
--- a/.github/workflows/codecov.yml
+++ b/.github/workflows/codecov.yml
@@ -18,6 +18,7 @@ jobs:
           - "8.1"
           - "8.2"
           - "8.3"
+          - "8.4"
 
     steps:
       - name: Checkout
diff --git a/.laminas-ci.json b/.laminas-ci.json
index 82cd446..29216fa 100644
--- a/.laminas-ci.json
+++ b/.laminas-ci.json
@@ -1,6 +1,3 @@
 {
-  "ignore_php_platform_requirements": {
-    "8.4": true
-  },
   "backwardCompatibilityCheck": true
 }
diff --git a/README.md b/README.md
index 2ef25fa..6fe050d 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,7 @@
 # dot-log
 
 ![OSS Lifecycle](https://img.shields.io/osslifecycle/dotkernel/dot-log)
-![PHP from Packagist (specify version)](https://img.shields.io/packagist/php-v/dotkernel/dot-log/4.1.0)
+![PHP from Packagist (specify version)](https://img.shields.io/packagist/php-v/dotkernel/dot-log/4.1.1)
 
 [![GitHub issues](https://img.shields.io/github/issues/dotkernel/dot-log)](https://github.com/dotkernel/dot-log/issues)
 [![GitHub forks](https://img.shields.io/github/forks/dotkernel/dot-log)](https://github.com/dotkernel/dot-log/network)
diff --git a/composer.json b/composer.json
index f9a8f45..c205fe4 100644
--- a/composer.json
+++ b/composer.json
@@ -26,7 +26,7 @@
     "require-dev": {
         "laminas/laminas-coding-standard": "^3.0",
         "phpunit/phpunit": "^10.2",
-        "vimeo/psalm": "^5.13"
+        "vimeo/psalm": "^6.0"
     },
     "autoload": {
         "psr-4": {
diff --git a/src/Formatter/Json.php b/src/Formatter/Json.php
index 8afb4b1..9713567 100644
--- a/src/Formatter/Json.php
+++ b/src/Formatter/Json.php
@@ -33,7 +33,7 @@ public function format(iterable $event): string
             $event['timestamp'] = $event['timestamp']->format($this->getDateTimeFormat());
         }
 
-        return json_encode(
+        return (string) json_encode(
             $event,
             JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE | JSON_NUMERIC_CHECK | JSON_PRESERVE_ZERO_FRACTION
         );