diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6acd57e..f592a29 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,14 +5,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 
-## [Unreleased]
+## [0.4.0] - 2022-05-24
 ### Added
 * Add support for document translation.
-### Changed
-### Deprecated
-### Removed
-### Fixed
-### Security
 
 
 ## [0.3.0] - 2022-05-18
@@ -39,7 +34,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 Initial version.
 
 
-[Unreleased]: https://github.com/DeepLcom/deepl-php/compare/v0.3.0...HEAD
+[0.4.0]: https://github.com/DeepLcom/deepl-php/compare/v0.3.0...v0.4.0
 [0.3.0]: https://github.com/DeepLcom/deepl-php/compare/v0.2.0...v0.3.0
 [0.2.0]: https://github.com/DeepLcom/deepl-php/compare/v0.1.1...v0.2.0
 [0.1.1]: https://github.com/DeepLcom/deepl-php/compare/v0.1.0...v0.1.1
diff --git a/VERSION b/VERSION
index 0d91a54..1d0ba9e 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-0.3.0
+0.4.0
diff --git a/src/Translator.php b/src/Translator.php
index 44d2018..9bcec77 100644
--- a/src/Translator.php
+++ b/src/Translator.php
@@ -15,7 +15,7 @@ class Translator
     /**
      * Library version.
      */
-    public const VERSION = '0.3.0';
+    public const VERSION = '0.4.0';
 
     /**
      * Implements all HTTP requests and retries.
@@ -49,7 +49,7 @@ public function __construct(string $authKey, array $options = [])
         $headers = array_replace(
             [
                 'Authorization' => "DeepL-Auth-Key $authKey",
-                'User-Agent' => 'deepl-php/0.3.0',
+                'User-Agent' => 'deepl-php/0.4.0',
             ],
             $options[TranslatorOptions::HEADERS] ?? []
         );