diff --git a/.travis.yml b/.travis.yml
index 1a159a8..1b5ca1c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,8 +1,8 @@
 language: php
 
 php:
-  - 5.6
-  - 7
+  - 7.1
+  - 7.2
 
 env:
   matrix:
diff --git a/README.md b/README.md
index fd00da9..1f22193 100644
--- a/README.md
+++ b/README.md
@@ -50,7 +50,7 @@ class User
 
 Requirements
 ------------
-Works with PHP 5.6 or PHP 7.
+Works with PHP 7.1 or higher.
 
 Submitting bugs and feature requests
 ------------------------------------
@@ -65,6 +65,9 @@ Thanks [Vašek Purchart](http://www.vasekpurchart.cz/) for ideas how to test Sym
 Changelog
 ----------
 
+## 3.0.0 (2018-01-07)
+- [#3](https://github.com/mhujer/jms-serializer-uuid-bundle/pull/3) Added Symfony 4.0 support, dropped support for Symfony 2. Requires PHP 7.1.
+
 ## 2.0.0 (2017-08-09)
 - [#1](https://github.com/mhujer/jms-serializer-uuid-bundle/pull/1) Support for JMS Serializer Bundle 2.0 (thanks @VasekPurchart !)
 
diff --git a/composer.json b/composer.json
index 8185186..2594433 100644
--- a/composer.json
+++ b/composer.json
@@ -18,19 +18,20 @@
 		}
 	],
 	"require": {
-		"jms/serializer-bundle": "~1.0|~2.0",
-		"mhujer/jms-serializer-uuid": "~1.0",
-		"symfony/config": "~2.7|~3.0",
-		"symfony/dependency-injection": "~2.7|~3.0",
-		"symfony/http-kernel": "~2.7|~3.0",
-		"symfony/yaml": "~2.7|~3.0"
+		"php": "^7.1",
+		"jms/serializer-bundle": "~1.0 || ~2.0",
+		"mhujer/jms-serializer-uuid": "~2.0",
+		"symfony/config": "~3.0 || ~4.0",
+		"symfony/dependency-injection": "~3.0 || ~4.0",
+		"symfony/http-kernel": "~3.0 || ~4.0",
+		"symfony/yaml": "~3.0 || ~4.0"
 	},
 	"require-dev": {
-		"consistence/coding-standard": "0.11",
+		"consistence/coding-standard": "2.3",
 		"jakub-onderka/php-parallel-lint": "0.9.2",
-		"matthiasnoback/symfony-dependency-injection-test": "0.7.6",
-		"phpunit/phpunit": "5.3.4",
-		"satooshi/php-coveralls": "1.0.1"
+		"matthiasnoback/symfony-dependency-injection-test": "2.3.0",
+		"phpunit/phpunit": "6.5.5",
+		"satooshi/php-coveralls": "2.0.0"
 	},
 	"autoload": {
 		"psr-4": { "Mhujer\\JmsSerializer\\Uuid\\SymfonyBundle\\": [ "src" ] },
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index be75d95..79ee404 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -2,14 +2,12 @@
 
 <phpunit
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-    xsi:noNamespaceSchemaLocation="http://schema.phpunit.de/5.3/phpunit.xsd"
+    xsi:noNamespaceSchemaLocation="http://schema.phpunit.de/6.5/phpunit.xsd"
     bootstrap="vendor/autoload.php"
     colors="true"
-    beStrictAboutTestsThatDoNotTestAnything="true"
     beStrictAboutChangesToGlobalState="true"
     beStrictAboutOutputDuringTests="true"
     beStrictAboutTodoAnnotatedTests="true"
-    checkForUnintentionallyCoveredCode="true"
     >
 
     <testsuites>
diff --git a/src/DependencyInjection/MhujerJmsSerializerUuidExtension.php b/src/DependencyInjection/MhujerJmsSerializerUuidExtension.php
index 6c143e2..de1f5f5 100644
--- a/src/DependencyInjection/MhujerJmsSerializerUuidExtension.php
+++ b/src/DependencyInjection/MhujerJmsSerializerUuidExtension.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types = 1);
+
 namespace Mhujer\JmsSerializer\Uuid\SymfonyBundle\DependencyInjection;
 
 use Symfony\Component\Config\FileLocator;
@@ -9,7 +11,7 @@
 class MhujerJmsSerializerUuidExtension extends \Symfony\Component\HttpKernel\DependencyInjection\Extension
 {
 
-	const ALIAS = 'mhujer_jms_serializer_uuid';
+	private const ALIAS = 'mhujer_jms_serializer_uuid';
 
 	/**
 	 * @param mixed[][] $configs
diff --git a/src/MhujerJmsSerializerUuidBundle.php b/src/MhujerJmsSerializerUuidBundle.php
index b161ff5..8f5f232 100644
--- a/src/MhujerJmsSerializerUuidBundle.php
+++ b/src/MhujerJmsSerializerUuidBundle.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types = 1);
+
 namespace Mhujer\JmsSerializer\Uuid\SymfonyBundle;
 
 class MhujerJmsSerializerUuidBundle extends \Symfony\Component\HttpKernel\Bundle\Bundle
diff --git a/tests/DependencyInjection/MhujerJmsSerializerUuidExtensionTest.php b/tests/DependencyInjection/MhujerJmsSerializerUuidExtensionTest.php
index 6bc8fbf..90eaa69 100644
--- a/tests/DependencyInjection/MhujerJmsSerializerUuidExtensionTest.php
+++ b/tests/DependencyInjection/MhujerJmsSerializerUuidExtensionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types = 1);
+
 namespace Mhujer\JmsSerializer\Uuid\SymfonyBundle\DependencyInjection;
 
 use Mhujer\JmsSerializer\Uuid\UuidSerializerHandler;