diff --git a/src/LocalesResolvers/Header.php b/src/LocalesResolvers/Header.php
index a0d65d8..8c74286 100644
--- a/src/LocalesResolvers/Header.php
+++ b/src/LocalesResolvers/Header.php
@@ -2,28 +2,19 @@
 
 namespace Contributte\Translation\LocalesResolvers;
 
-use Contributte\Translation\Exceptions\InvalidArgument;
 use Contributte\Translation\Translator;
 use Nette\Http\IRequest;
-use Nette\Http\Request;
 use Nette\Utils\Strings;
 
 class Header implements ResolverInterface
 {
 
-	private Request $httpRequest;
+	private IRequest $httpRequest;
 
-	/**
-	 * @throws \Contributte\Translation\Exceptions\InvalidArgument
-	 */
 	public function __construct(
 		IRequest $httpRequest
 	)
 	{
-		if (!is_a($httpRequest, Request::class, true)) {
-			throw new InvalidArgument('Header locale resolver need "Nette\\Http\\Request" or his child for using "detectLanguage" method.');
-		}
-
 		$this->httpRequest = $httpRequest;
 	}
 
@@ -31,24 +22,61 @@ public function resolve(
 		Translator $translator
 	): ?string
 	{
-		/** @var array<string> $langs */
-		$langs = [];
+		/** @var array<string> $locales */
+		$locales = [];
 
 		foreach ($translator->getAvailableLocales() as $v1) {
-			$langs[] = $v1;
+			$locales[] = $v1;
 
 			if (Strings::length($v1) < 3) {
 				continue;
 			}
 
-			$langs[] = Strings::substring($v1, 0, 2);// en_US => en
+			$locales[] = Strings::substring($v1, 0, 2);// en_US => en
 		}
 
-		if (count($langs) === 0) {
+		if (count($locales) === 0) {
 			return null;
 		}
 
-		return $this->httpRequest->detectLanguage($langs);
+		return $this->detectLocale($locales);
+	}
+
+	/**
+	 * This function is a copy of \Nette\Http\Request::detectLanguage()
+	 * Returns the most preferred locale by browser. Uses the `Accept-Language` header. If no match is reached, it returns `null`.
+	 *
+	 * @param array<string> $supportedLocales
+	 */
+	private function detectLocale(array $supportedLocales): ?string
+	{
+		$header = $this->httpRequest->getHeader('Accept-Language');
+		if ($header === null) {
+			return null;
+		}
+
+		rsort($supportedLocales); // first more specific
+		preg_match_all(
+			'#(' . implode('|', $supportedLocales) . ')(?:-[^\s,;=]+)?\s*(?:;\s*q=([0-9.]+))?#',
+			strtr(strtolower($header), '_', '-'), // CS_CZ -> cs-CZ
+			$matches
+		);
+
+		if (count($matches) === 0) {
+			return null;
+		}
+
+		$max = 0;
+		$locale = null;
+		foreach ($matches[1] as $key => $value) {
+			$q = $matches[2][$key] === '' ? 1.0 : (float) $matches[2][$key];
+			if ($q > $max) {
+				$max = $q;
+				$locale = $value;
+			}
+		}
+
+		return $locale;
 	}
 
 }
diff --git a/tests/Tests/LocalesResolvers/HeaderTest.phpt b/tests/Tests/LocalesResolvers/HeaderTest.phpt
index 4a44e2b..d932539 100644
--- a/tests/Tests/LocalesResolvers/HeaderTest.phpt
+++ b/tests/Tests/LocalesResolvers/HeaderTest.phpt
@@ -2,13 +2,10 @@
 
 namespace Tests\LocalesResolvers;
 
-use Contributte\Translation\Exceptions\InvalidArgument;
 use Contributte\Translation\LocalesResolvers\Header;
 use Contributte\Translation\Translator;
 use Mockery;
-use Nette\Http\IRequest;
 use Nette\Http\Request;
-use Nette\Http\UrlImmutable;
 use Nette\Http\UrlScript;
 use Tester\Assert;
 use Tests\TestAbstract;
@@ -31,137 +28,6 @@ final class HeaderTest extends TestAbstract
 		Assert::same('en-us', $this->resolve('da, en_us', ['en', 'en-us']));
 	}
 
-	public function test02(): void
-	{
-		Assert::exception(static function (): void {
-			new Header(new class implements IRequest {
-
-				public function getReferer(): ?UrlImmutable
-				{
-					return null;
-				}
-
-				public function isSameSite(): bool
-				{
-					return true;
-				}
-
-				public function getUrl(): UrlScript
-				{
-					return new UrlScript();
-				}
-
-				/**
-				 * @return mixed
-				 */
-				public function getQuery(
-					?string $key = null
-				)
-				{
-					return null;
-				}
-
-				/**
-				 * @return mixed
-				 */
-				public function getPost(
-					?string $key = null
-				)
-				{
-					return null;
-				}
-
-				/**
-				 * @return mixed
-				 */
-				public function getFile(
-					string $key
-				)
-				{
-					return null;
-				}
-
-				/**
-				 * @return array<\Nette\Http\FileUpload>
-				 */
-				public function getFiles(): array
-				{
-					return [];
-				}
-
-				/**
-				 * @return mixed
-				 */
-				public function getCookie(
-					string $key
-				)
-				{
-					return null;
-				}
-
-				/**
-				 * @return array<string>
-				 */
-				public function getCookies(): array
-				{
-					return [];
-				}
-
-				public function getMethod(): string
-				{
-					return '';
-				}
-
-				public function isMethod(
-					string $method
-				): bool
-				{
-					return true;
-				}
-				public function getHeader(
-					string $header
-				): ?string
-				{
-					return null;
-				}
-
-				/**
-				 * @return array<string>
-				 */
-				public function getHeaders(): array
-				{
-					return [];
-				}
-
-				public function isSecured(): bool
-				{
-					return true;
-				}
-
-				public function isAjax(): bool
-				{
-					return true;
-				}
-
-				public function getRemoteAddress(): ?string
-				{
-					return null;
-				}
-
-				public function getRemoteHost(): ?string
-				{
-					return null;
-				}
-
-				public function getRawBody(): ?string
-				{
-					return null;
-				}
-
-			});
-		}, InvalidArgument::class, 'Header locale resolver need "' . Request::class . '" or his child for using "detectLanguage" method.');
-	}
-
 	/**
 	 * @param array<string> $availableLocales
 	 */