diff --git a/composer.json b/composer.json
index 070860c..905022b 100644
--- a/composer.json
+++ b/composer.json
@@ -17,21 +17,21 @@
     "ext-openssl": "*",
     "guzzlehttp/guzzle": "~6.0|~7.0",
     "minishlink/web-push": "~4.0|~5.0|~6.0",
-    "symfony/http-kernel": "~3.0|~4.0|~5.0"
+    "symfony/http-kernel": "~3.0|~4.0|~5.0|~6.0"
   },
   "require-dev": {
     "bentools/doctrine-static": "1.0.x-dev",
     "doctrine/dbal": "~2.5 <=2.9",
-    "nyholm/symfony-bundle-test": "~1.4",
-    "phpunit/phpunit": "~5.0|~6.0|~7.0",
-    "symfony/config": "~4.0",
-    "symfony/dependency-injection": "~3.0|~4.0|~5.0",
-    "symfony/framework-bundle": "~3.0|~4.0|~5.0",
-    "symfony/http-foundation": "~3.0|~4.0|~5.0",
-    "symfony/routing": "~3.0|~4.0|~5.0",
-    "symfony/security": "~3.0|~4.0|~5.0",
-    "symfony/var-dumper": "~3.0|~4.0|~5.0",
-    "symfony/yaml": "~3.0|~4.0|~5.0",
+    "nyholm/symfony-bundle-test": "~1.8",
+    "phpunit/phpunit": "~5.0|~6.0|~7.0|~8.0|~9.0",
+    "symfony/config": "~4.0|~5.0|~6.0",
+    "symfony/dependency-injection": "~3.0|~4.0|~5.0|~6.0",
+    "symfony/framework-bundle": "~3.0|~4.0|~5.0|~6.0",
+    "symfony/http-foundation": "~3.0|~4.0|~5.0|~6.0",
+    "symfony/routing": "~3.0|~4.0|~5.0|~6.0",
+    "symfony/security": "~3.0|~4.0|~5.0|~6.0",
+    "symfony/var-dumper": "~3.0|~4.0|~5.0|~6.0",
+    "symfony/yaml": "~3.0|~4.0|~5.0|~6.0",
     "twig/twig": "~1.0|~2.0"
   },
   "autoload": {
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 4e9f6b1..4bd0fd2 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -6,6 +6,7 @@
          backupGlobals="false"
          colors="true"
          bootstrap="vendor/autoload.php"
+         cacheResult ="false"
 >
     <php>
         <ini name="error_reporting" value="-1" />
diff --git a/src/Sender/RequestBuilder.php b/src/Sender/RequestBuilder.php
index 3ff45ae..6ee13e8 100644
--- a/src/Sender/RequestBuilder.php
+++ b/src/Sender/RequestBuilder.php
@@ -6,7 +6,7 @@
 use BenTools\WebPushBundle\Model\Message\PushMessage;
 use BenTools\WebPushBundle\Model\Subscription\UserSubscriptionInterface;
 use GuzzleHttp\Psr7\Request;
-use function GuzzleHttp\Psr7\stream_for;
+use GuzzleHttp\Psr7\Utils as GuzzleUtils;
 use GuzzleHttp\Psr7\Uri;
 use Minishlink\WebPush\Encryption;
 use Minishlink\WebPush\Utils;
@@ -56,7 +56,7 @@ public function createRequest(
             $content = $encryptionContentCodingHeader.$encrypted['cipherText'];
 
             return $request
-                ->withBody(stream_for($content))
+                ->withBody(GuzzleUtils::streamFor($content))
                 ->withHeader('Content-Length', Utils::safeStrlen($content));
         }
 
diff --git a/src/WebPushBundle.php b/src/WebPushBundle.php
index 70147e6..b3fdd34 100644
--- a/src/WebPushBundle.php
+++ b/src/WebPushBundle.php
@@ -5,6 +5,7 @@
 use BenTools\WebPushBundle\DependencyInjection\WebPushCompilerPass;
 use BenTools\WebPushBundle\DependencyInjection\WebPushExtension;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\Extension\ExtensionInterface;
 use Symfony\Component\HttpKernel\Bundle\Bundle;
 
 class WebPushBundle extends Bundle
@@ -12,7 +13,7 @@ class WebPushBundle extends Bundle
     /**
      * {@inheritdoc}
      */
-    public function getContainerExtension()
+    public function getContainerExtension(): ?ExtensionInterface
     {
         return new WebPushExtension();
     }
diff --git a/tests/BundleTest.php b/tests/BundleTest.php
index 87dc87b..fff0412 100644
--- a/tests/BundleTest.php
+++ b/tests/BundleTest.php
@@ -9,7 +9,7 @@
 
 final class BundleTest extends KernelTestCase
 {
-    protected function setUp()
+    protected function setUp(): void
     {
         static::bootKernel();
     }
@@ -38,10 +38,10 @@ public function manager_is_found()
 
     /**
      * @test
-     * @expectedException \InvalidArgumentException
      */
     public function unknown_manager_raises_exception()
     {
+        $this->expectException(\InvalidArgumentException::class);
         self::$kernel->getContainer()->get(UserSubscriptionManagerRegistry::class)->getManager(Foo::class);
     }
 }
diff --git a/tests/RegistrationTest.php b/tests/RegistrationTest.php
index 9d8eb70..b18911c 100644
--- a/tests/RegistrationTest.php
+++ b/tests/RegistrationTest.php
@@ -11,7 +11,7 @@
 
 final class RegistrationTest extends KernelTestCase
 {
-    protected function setUp()
+    protected function setUp(): void
     {
         static::bootKernel();
     }
@@ -30,7 +30,6 @@ public function registration_works()
         $em->flush();
         $this->assertNotNull($em->find(TestUser::class, 'bob'));
 
-
         $register = self::$kernel->getContainer()->get(RegisterSubscriptionAction::class);
 
         $rawSubscriptionData = [