diff --git a/src/User/Sign.php b/src/User/Sign.php
index edb07d1..9b228d5 100644
--- a/src/User/Sign.php
+++ b/src/User/Sign.php
@@ -26,6 +26,11 @@ class Sign
 
 	private Logger $logger;
 
+	/**
+	 * @var array<string, mixed>
+	 */
+	private array $default_parameters = [];
+
 
 	public function __construct(Settings $settings, Connection $connection, Url $url, Configuration $configuration, Language $language, Logger $logger)
 	{
@@ -37,6 +42,14 @@ public function __construct(Settings $settings, Connection $connection, Url $url
 		$this->logger = $logger;
 	}
 
+	/**
+	 * @param array<array-key, mixed> $parameters
+	 */
+	public function setDefaultParameters(array $parameters): void
+	{
+		$this->default_parameters = $parameters;
+	}
+
 
 	/**
 	 * @param array<string, mixed> $parameters
@@ -51,9 +64,13 @@ public function authenticate(bool $reload = false, array $parameters = []): ?str
 			'application_product' => $this->configuration->product(),
 			'application_language' => $this->language->get(),
 			'application_version' => $this->configuration->version(),
-			'application_parameters' => array_merge([
-				'guest' => $token === null,
-			], $parameters),
+			'application_parameters' => array_merge(
+				$this->default_parameters,
+				$parameters,
+				[
+					'guest' => $token === null,
+				],
+			),
 		], $token ?? '');
 	}
 
diff --git a/tests/User/SignTestJwt.phpt b/tests/User/SignTestJwt.phpt
new file mode 100644
index 0000000..66f214a
--- /dev/null
+++ b/tests/User/SignTestJwt.phpt
@@ -0,0 +1,109 @@
+<?php declare(strict_types=1);
+
+namespace BulkGate\Plugin\User\Test;
+
+/**
+ * @author Lukáš Piják 2023 TOPefekt s.r.o.
+ * @link https://www.bulkgate.com/
+ */
+
+use Mockery;
+use Tester\{Assert, TestCase};
+use BulkGate\Plugin\{Debug\Logger,
+	Eshop\ConfigurationDefault,
+	IO\Connection,
+	IO\Url,
+	Localization\Language,
+	Settings\Settings,
+	User\Sign,
+	Utils\Jwt};
+
+require_once __DIR__ . '/../bootstrap.php';
+
+/**
+ * @testCase
+ */
+class SignTest extends TestCase
+{
+	public function testDefaultParameters(): void
+	{
+		$sign = new Sign($settings = Mockery::mock(Settings::class), Mockery::mock(Connection::class), new Url(), new ConfigurationDefault('url', 'eshop', '1.0', 'Test Eshop'), $language = Mockery::mock(Language::class), Mockery::mock(Logger::class));
+		$sign->setDefaultParameters(['test1' => 'default_test1', 'test3' => 'default_test3']);
+
+		$settings->shouldReceive('load')->with('static:application_token', true)->andReturn('test_application_token');
+		$settings->shouldReceive('load')->with('static:application_id')->andReturn(12345);
+		$language->shouldReceive('get')->withNoArgs()->once()->andReturn('cs');
+
+		$jwt = Mockery::mock('overload:' . Jwt::class);
+		$jwt->shouldReceive('encode')->with([
+			'application_id' => 12345,
+			'application_installation' => 'url',
+			'application_product' => 'eshop',
+			'application_language' => 'cs',
+			'application_version' => '1.0',
+			'application_parameters' => [
+				'guest' => false,
+				'test1' => 'test1',
+				'test2' => 'test2',
+				'test3' => 'default_test3'
+			]
+		], 'test_application_token')->once()->andReturn('0.0.0');
+
+
+		Assert::match('~^[A-Za-z0-9\-_]+\.[A-Za-z0-9\-_]+\.[A-Za-z0-9\-_]+$~', $sign->authenticate(true, ['test1' => 'test1', 'test2' => 'test2']));
+	}
+
+	public function testGuestParameterOverride(): void
+	{
+		$sign = new Sign($settings = Mockery::mock(Settings::class), Mockery::mock(Connection::class), new Url(), new ConfigurationDefault('url', 'eshop', '1.0', 'Test Eshop'), $language = Mockery::mock(Language::class), Mockery::mock(Logger::class));
+
+		$settings->shouldReceive('load')->with('static:application_token', true)->andReturn('test_application_token');
+		$settings->shouldReceive('load')->with('static:application_id')->andReturn(12345);
+		$language->shouldReceive('get')->withNoArgs()->once()->andReturn('cs');
+
+		$jwt = Mockery::mock('overload:' . Jwt::class);
+		$jwt->shouldReceive('encode')->with([
+			'application_id' => 12345,
+			'application_installation' => 'url',
+			'application_product' => 'eshop',
+			'application_language' => 'cs',
+			'application_version' => '1.0',
+			'application_parameters' => [
+				'guest' => false,
+			]
+		], 'test_application_token')->once()->andReturn('0.0.0');
+
+		Assert::match('~^[A-Za-z0-9\-_]+\.[A-Za-z0-9\-_]+\.[A-Za-z0-9\-_]+$~', $sign->authenticate(true, ['guest' => 'someValue']));
+	}
+
+	public function testGuestParameterNullToken(): void
+	{
+		$sign = new Sign($settings = Mockery::mock(Settings::class), Mockery::mock(Connection::class), new Url(), new ConfigurationDefault('url', 'eshop', '1.0', 'Test Eshop'), $language = Mockery::mock(Language::class), Mockery::mock(Logger::class));
+
+		$settings->shouldReceive('load')->with('static:application_token', false)->andReturn(null);
+		$settings->shouldReceive('load')->with('static:application_id')->andReturn(12345);
+		$language->shouldReceive('get')->withNoArgs()->once()->andReturn('cs');
+
+		$jwt = Mockery::mock('overload:' . Jwt::class);
+		$jwt->shouldReceive('encode')->with([
+			'application_id' => 12345,
+			'application_installation' => 'url',
+			'application_product' => 'eshop',
+			'application_language' => 'cs',
+			'application_version' => '1.0',
+			'application_parameters' => [
+				'guest' => true,
+			]
+		], '')->once()->andReturn('0.0.0');
+
+		Assert::match('~^[A-Za-z0-9\-_]+\.[A-Za-z0-9\-_]+\.[A-Za-z0-9\-_]+$~', $sign->authenticate());
+	}
+
+
+	public function tearDown(): void
+	{
+		Mockery::close();
+	}
+}
+
+(new SignTest())->run();