diff --git a/.php-cs-fixer.dist.php b/.php-cs-fixer.dist.php
index 583be2ac59..fdb481fd19 100644
--- a/.php-cs-fixer.dist.php
+++ b/.php-cs-fixer.dist.php
@@ -11,6 +11,7 @@ return (new PhpCsFixer\Config())
         '@Symfony' => true,
         '@Symfony:risky' => true,
         'protected_to_private' => false,
+        'nullable_type_declaration_for_default_null_value' => ['use_nullable_type_declaration' => false],
     ])
     ->setRiskyAllowed(true)
     ->setFinder(
diff --git a/src/Symfony/Bridge/Doctrine/Tests/ManagerRegistryTest.php b/src/Symfony/Bridge/Doctrine/Tests/ManagerRegistryTest.php
index 5ddd60df8e..a004935a6a 100644
--- a/src/Symfony/Bridge/Doctrine/Tests/ManagerRegistryTest.php
+++ b/src/Symfony/Bridge/Doctrine/Tests/ManagerRegistryTest.php
@@ -19,9 +19,6 @@ class ManagerRegistryTest extends TestCase
 {
     public static function setUpBeforeClass(): void
     {
-        if (!class_exists(\PHPUnit_Framework_TestCase::class)) {
-            self::markTestSkipped('proxy-manager-bridge is not yet compatible with namespaced phpunit versions.');
-        }
         $test = new PhpDumperTest();
         $test->testDumpContainerWithProxyServiceWillShareProxies();
     }
diff --git a/src/Symfony/Bundle/FrameworkBundle/Tests/Functional/app/CachePools/bundles.php b/src/Symfony/Bundle/FrameworkBundle/Tests/Functional/app/CachePools/bundles.php
index 2e46e896bc..13ab9fddee 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Tests/Functional/app/CachePools/bundles.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Tests/Functional/app/CachePools/bundles.php
@@ -10,7 +10,6 @@
  */
 
 use Symfony\Bundle\FrameworkBundle\FrameworkBundle;
-use Symfony\Bundle\FrameworkBundle\Tests\Functional\Bundle\TestBundle\TestBundle;
 
 return [
     new FrameworkBundle(),
diff --git a/src/Symfony/Component/Cache/Tests/Adapter/ArrayAdapterTest.php b/src/Symfony/Component/Cache/Tests/Adapter/ArrayAdapterTest.php
index 9292b1c962..5ed33cee77 100644
--- a/src/Symfony/Component/Cache/Tests/Adapter/ArrayAdapterTest.php
+++ b/src/Symfony/Component/Cache/Tests/Adapter/ArrayAdapterTest.php
@@ -49,7 +49,7 @@ class ArrayAdapterTest extends AdapterTestCase
 
         // Fail (should be missing from $values)
         $item = $cache->getItem('buz');
-        $cache->save($item->set(function() {}));
+        $cache->save($item->set(function () {}));
 
         $values = $cache->getValues();
 
diff --git a/src/Symfony/Component/Config/Tests/Definition/Builder/ExprBuilderTest.php b/src/Symfony/Component/Config/Tests/Definition/Builder/ExprBuilderTest.php
index 74ae972e54..bec4275404 100644
--- a/src/Symfony/Component/Config/Tests/Definition/Builder/ExprBuilderTest.php
+++ b/src/Symfony/Component/Config/Tests/Definition/Builder/ExprBuilderTest.php
@@ -225,7 +225,7 @@ class ExprBuilderTest extends TestCase
      *
      * @return array The finalized config values
      */
-    protected function finalizeTestBuilder(NodeDefinition $nodeDefinition, ?array $config = null): array
+    protected function finalizeTestBuilder(NodeDefinition $nodeDefinition, array $config = null): array
     {
         return $nodeDefinition
             ->end()
diff --git a/src/Symfony/Component/Config/Tests/Resource/ReflectionClassResourceTest.php b/src/Symfony/Component/Config/Tests/Resource/ReflectionClassResourceTest.php
index 8ba3a8c2c9..e097205e8c 100644
--- a/src/Symfony/Component/Config/Tests/Resource/ReflectionClassResourceTest.php
+++ b/src/Symfony/Component/Config/Tests/Resource/ReflectionClassResourceTest.php
@@ -64,7 +64,7 @@ class ReflectionClassResourceTest extends TestCase
     /**
      * @dataProvider provideHashedSignature
      */
-    public function testHashedSignature(bool $changeExpected, int $changedLine, ?string $changedCode, ?\Closure $setContext = null)
+    public function testHashedSignature(bool $changeExpected, int $changedLine, ?string $changedCode, \Closure $setContext = null)
     {
         if ($setContext) {
             $setContext();
diff --git a/src/Symfony/Component/HttpFoundation/Tests/Session/Storage/Handler/MemcachedSessionHandlerTest.php b/src/Symfony/Component/HttpFoundation/Tests/Session/Storage/Handler/MemcachedSessionHandlerTest.php
index a7f7e8f817..200567a29d 100644
--- a/src/Symfony/Component/HttpFoundation/Tests/Session/Storage/Handler/MemcachedSessionHandlerTest.php
+++ b/src/Symfony/Component/HttpFoundation/Tests/Session/Storage/Handler/MemcachedSessionHandlerTest.php
@@ -40,7 +40,7 @@ class MemcachedSessionHandlerTest extends TestCase
 
         $r = new \ReflectionClass(\Memcached::class);
         $methodsToMock = array_map(function ($m) { return $m->name; }, $r->getMethods(\ReflectionMethod::IS_PUBLIC));
-        $methodsToMock = array_diff($methodsToMock, ['getDelayed','getDelayedByKey']);
+        $methodsToMock = array_diff($methodsToMock, ['getDelayed', 'getDelayedByKey']);
 
         $this->memcached = $this->getMockBuilder(\Memcached::class)
             ->disableOriginalConstructor()
diff --git a/src/Symfony/Component/Mailer/Transport/Dsn.php b/src/Symfony/Component/Mailer/Transport/Dsn.php
index cc25f7a237..04d3540f7b 100644
--- a/src/Symfony/Component/Mailer/Transport/Dsn.php
+++ b/src/Symfony/Component/Mailer/Transport/Dsn.php
@@ -25,7 +25,7 @@ final class Dsn
     private $port;
     private $options;
 
-    public function __construct(string $scheme, string $host, ?string $user = null, ?string $password = null, ?int $port = null, array $options = [])
+    public function __construct(string $scheme, string $host, string $user = null, string $password = null, int $port = null, array $options = [])
     {
         $this->scheme = $scheme;
         $this->host = $host;
diff --git a/src/Symfony/Component/Yaml/Exception/ParseException.php b/src/Symfony/Component/Yaml/Exception/ParseException.php
index c75066da2d..82c05a714f 100644
--- a/src/Symfony/Component/Yaml/Exception/ParseException.php
+++ b/src/Symfony/Component/Yaml/Exception/ParseException.php
@@ -24,10 +24,10 @@ class ParseException extends RuntimeException
     private $rawMessage;
 
     /**
-     * @param string          $message    The error message
-     * @param int             $parsedLine The line where the error occurred
-     * @param string|null     $snippet    The snippet of code near the problem
-     * @param string|null     $parsedFile The file name where the error occurred
+     * @param string      $message    The error message
+     * @param int         $parsedLine The line where the error occurred
+     * @param string|null $snippet    The snippet of code near the problem
+     * @param string|null $parsedFile The file name where the error occurred
      */
     public function __construct(string $message, int $parsedLine = -1, string $snippet = null, string $parsedFile = null, \Throwable $previous = null)
     {