diff --git a/DebugClassLoader.php b/DebugClassLoader.php
index 69c28c1..1b4aae1 100644
--- a/DebugClassLoader.php
+++ b/DebugClassLoader.php
@@ -21,6 +21,7 @@
 use Prophecy\Prophecy\ProphecySubjectInterface;
 use ProxyManager\Proxy\ProxyInterface;
 use Symfony\Component\ErrorHandler\Internal\TentativeTypes;
+use Symfony\Component\HttpClient\HttplugClient;
 use Symfony\Component\VarExporter\LazyObjectInterface;
 
 /**
@@ -421,7 +422,9 @@ public function checkAnnotations(\ReflectionClass $refl, string $class): array
             if (!isset(self::$checkedClasses[$use])) {
                 $this->checkClass($use);
             }
-            if (isset(self::$deprecated[$use]) && strncmp($vendor, str_replace('_', '\\', $use), $vendorLen) && !isset(self::$deprecated[$class])) {
+            if (isset(self::$deprecated[$use]) && strncmp($vendor, str_replace('_', '\\', $use), $vendorLen) && !isset(self::$deprecated[$class])
+                && !(HttplugClient::class === $class && \in_array($use, [\Http\Message\RequestFactory::class, \Http\Message\StreamFactory::class, \Http\Message\UriFactory::class], true))
+            ) {
                 $type = class_exists($class, false) ? 'class' : (interface_exists($class, false) ? 'interface' : 'trait');
                 $verb = class_exists($use, false) || interface_exists($class, false) ? 'extends' : (interface_exists($use, false) ? 'implements' : 'uses');
 
@@ -1129,7 +1132,20 @@ private function fixReturnStatements(\ReflectionMethod $method, string $returnTy
         }
 
         $end = $method->isGenerator() ? $i : $method->getEndLine();
+        $inClosure = false;
+        $braces = 0;
         for (; $i < $end; ++$i) {
+            if (!$inClosure) {
+                $inClosure = str_contains($code[$i], 'function (');
+            }
+
+            if ($inClosure) {
+                $braces += substr_count($code[$i], '{') - substr_count($code[$i], '}');
+                $inClosure = $braces > 0;
+
+                continue;
+            }
+
             if ('void' === $returnType) {
                 $fixedCode[$i] = str_replace('    return null;', '    return;', $code[$i]);
             } elseif ('mixed' === $returnType || '?' === $returnType[0]) {
diff --git a/ErrorRenderer/SerializerErrorRenderer.php b/ErrorRenderer/SerializerErrorRenderer.php
index 8130b2e..1f286b7 100644
--- a/ErrorRenderer/SerializerErrorRenderer.php
+++ b/ErrorRenderer/SerializerErrorRenderer.php
@@ -44,7 +44,7 @@ public function __construct(SerializerInterface $serializer, string|callable $fo
 
     public function render(\Throwable $exception): FlattenException
     {
-        $headers = [];
+        $headers = ['Vary' => 'Accept'];
         $debug = \is_bool($this->debug) ? $this->debug : ($this->debug)($exception);
         if ($debug) {
             $headers['X-Debug-Exception'] = rawurlencode($exception->getMessage());
@@ -55,19 +55,17 @@ public function render(\Throwable $exception): FlattenException
 
         try {
             $format = \is_string($this->format) ? $this->format : ($this->format)($flattenException);
-            $headers = [
-                'Content-Type' => Request::getMimeTypes($format)[0] ?? $format,
-                'Vary' => 'Accept',
-            ];
+            $headers['Content-Type'] = Request::getMimeTypes($format)[0] ?? $format;
 
-            return $flattenException->setAsString($this->serializer->serialize($flattenException, $format, [
+            $flattenException->setAsString($this->serializer->serialize($flattenException, $format, [
                 'exception' => $exception,
                 'debug' => $debug,
-            ]))
-            ->setHeaders($flattenException->getHeaders() + $headers);
+            ]));
         } catch (NotEncodableValueException) {
-            return $this->fallbackErrorRenderer->render($exception);
+            $flattenException = $this->fallbackErrorRenderer->render($exception);
         }
+
+        return $flattenException->setHeaders($flattenException->getHeaders() + $headers);
     }
 
     public static function getPreferredFormat(RequestStack $requestStack): \Closure
diff --git a/LICENSE b/LICENSE
index 5c7ba05..f37c76b 100644
--- a/LICENSE
+++ b/LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2019-2023 Fabien Potencier
+Copyright (c) 2019-present Fabien Potencier
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
diff --git a/Resources/views/error.html.php b/Resources/views/error.html.php
index fccbc08..a1624ea 100644
--- a/Resources/views/error.html.php
+++ b/Resources/views/error.html.php
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
 <head>
     <meta charset="<?= $this->charset; ?>" />
     <meta name="robots" content="noindex,nofollow,noarchive" />
diff --git a/Tests/DebugClassLoaderTest.php b/Tests/DebugClassLoaderTest.php
index ab2ea41..edb5851 100644
--- a/Tests/DebugClassLoaderTest.php
+++ b/Tests/DebugClassLoaderTest.php
@@ -140,7 +140,7 @@ class_exists('Test\\'.__NAMESPACE__.'\\'.$class, true);
         $this->assertSame($xError, $lastError);
     }
 
-    public function provideDeprecatedSuper(): array
+    public static function provideDeprecatedSuper(): array
     {
         return [
             ['DeprecatedInterfaceClass', 'DeprecatedInterface', 'implements'],
diff --git a/Tests/ErrorEnhancer/ClassNotFoundErrorEnhancerTest.php b/Tests/ErrorEnhancer/ClassNotFoundErrorEnhancerTest.php
index 1ca2f16..72ee199 100644
--- a/Tests/ErrorEnhancer/ClassNotFoundErrorEnhancerTest.php
+++ b/Tests/ErrorEnhancer/ClassNotFoundErrorEnhancerTest.php
@@ -72,7 +72,7 @@ public function testEnhance(string $originalMessage, string $enhancedMessage, $a
         $this->assertSame($expectedLine, $error->getLine());
     }
 
-    public function provideClassNotFoundData()
+    public static function provideClassNotFoundData()
     {
         $autoloader = new ComposerClassLoader();
         $autoloader->add('Symfony\Component\ErrorHandler\Error\\', realpath(__DIR__.'/../../Error'));
diff --git a/Tests/ErrorEnhancer/UndefinedFunctionErrorEnhancerTest.php b/Tests/ErrorEnhancer/UndefinedFunctionErrorEnhancerTest.php
index fe7d537..547e333 100644
--- a/Tests/ErrorEnhancer/UndefinedFunctionErrorEnhancerTest.php
+++ b/Tests/ErrorEnhancer/UndefinedFunctionErrorEnhancerTest.php
@@ -34,7 +34,7 @@ public function testEnhance(string $originalMessage, string $enhancedMessage)
         $this->assertSame($expectedLine, $error->getLine());
     }
 
-    public function provideUndefinedFunctionData()
+    public static function provideUndefinedFunctionData()
     {
         return [
             [
diff --git a/Tests/ErrorEnhancer/UndefinedMethodErrorEnhancerTest.php b/Tests/ErrorEnhancer/UndefinedMethodErrorEnhancerTest.php
index b31c6c2..f417200 100644
--- a/Tests/ErrorEnhancer/UndefinedMethodErrorEnhancerTest.php
+++ b/Tests/ErrorEnhancer/UndefinedMethodErrorEnhancerTest.php
@@ -33,7 +33,7 @@ public function testEnhance(string $originalMessage, string $enhancedMessage)
         $this->assertSame($expectedLine, $error->getLine());
     }
 
-    public function provideUndefinedMethodData()
+    public static function provideUndefinedMethodData()
     {
         return [
             [
diff --git a/Tests/ErrorHandlerTest.php b/Tests/ErrorHandlerTest.php
index a45e8e1..3926b73 100644
--- a/Tests/ErrorHandlerTest.php
+++ b/Tests/ErrorHandlerTest.php
@@ -402,7 +402,7 @@ public function testHandleException(string $expectedMessage, \Throwable $excepti
         }
     }
 
-    public function handleExceptionProvider(): array
+    public static function handleExceptionProvider(): array
     {
         return [
             ['Uncaught Exception: foo', new \Exception('foo')],
@@ -602,7 +602,7 @@ public function testErrorHandlerWhenLogging(bool $previousHandlerWasDefined, boo
         }
     }
 
-    public function errorHandlerWhenLoggingProvider(): iterable
+    public static function errorHandlerWhenLoggingProvider(): iterable
     {
         foreach ([false, true] as $previousHandlerWasDefined) {
             foreach ([false, true] as $loggerSetsAnotherHandler) {
diff --git a/Tests/ErrorRenderer/HtmlErrorRendererTest.php b/Tests/ErrorRenderer/HtmlErrorRendererTest.php
index f292d0f..6680b95 100644
--- a/Tests/ErrorRenderer/HtmlErrorRendererTest.php
+++ b/Tests/ErrorRenderer/HtmlErrorRendererTest.php
@@ -24,7 +24,7 @@ public function testRender(\Throwable $exception, HtmlErrorRenderer $errorRender
         $this->assertStringMatchesFormat($expected, $errorRenderer->render($exception)->getAsString());
     }
 
-    public function getRenderData(): iterable
+    public static function getRenderData(): iterable
     {
         $expectedDebug = <<<HTML
 <!-- Foo (500 Internal Server Error) -->
@@ -37,7 +37,7 @@ public function getRenderData(): iterable
 
         $expectedNonDebug = <<<HTML
 <!DOCTYPE html>
-<html>
+<html lang="en">
 %A<title>An Error Occurred: Internal Server Error</title>
 %A<h2>The server returned a "500 Internal Server Error".</h2>%A
 HTML;
diff --git a/Tests/Exception/FlattenExceptionTest.php b/Tests/Exception/FlattenExceptionTest.php
index 298fb67..b1fadb4 100644
--- a/Tests/Exception/FlattenExceptionTest.php
+++ b/Tests/Exception/FlattenExceptionTest.php
@@ -226,7 +226,7 @@ public function testCreate()
         );
     }
 
-    public function flattenDataProvider(): array
+    public static function flattenDataProvider(): array
     {
         return [
             [new \Exception('test', 123), 'Exception'],
@@ -234,7 +234,7 @@ public function flattenDataProvider(): array
         ];
     }
 
-    public function stringAndIntDataProvider(): array
+    public static function stringAndIntDataProvider(): array
     {
         return [
             [new \Exception('test1', 123)],