diff --git a/src/Dibi/Connection.php b/src/Dibi/Connection.php
index ee1a026c..b3697ebd 100644
--- a/src/Dibi/Connection.php
+++ b/src/Dibi/Connection.php
@@ -533,9 +533,39 @@ public function substitute(string $value): string
 	/**
 	 * @param  callable(object): Expression  $translator
 	 */
-	public function setObjectTranslator(string $class, callable $translator): void
+	public function setObjectTranslator(callable $translator): void
 	{
-		$this->translators[$class] = $translator;
+		if (!$translator instanceof \Closure) {
+			$translator = \Closure::fromCallable($translator);
+		}
+
+		$param = (new \ReflectionFunction($translator))->getParameters();
+		if (count($param) !== 1) {
+			throw new Exception('Object translator must have exactly one parameter.');
+		}
+
+		$name = '$' . $param[0]->getName();
+		$type = $param[0]->getType();
+		if ($type === null) {
+			throw new Exception("Object translator parameter '$name' must be declared with typehint.");
+		} elseif ($type->allowsNull()) {
+			throw new Exception("Object translator parameter '$name' must not be nullable.");
+		}
+
+		if ($type instanceof \ReflectionNamedType) {
+			$types = [$type];
+		} elseif ($type instanceof \ReflectionUnionType) {
+			$types = $type->getTypes();
+		} else {
+			throw new Exception("Object translator parameter '$name' type must be simple or union.");
+		}
+
+		foreach ($types as $type) {
+			if ($type->isBuiltin()) {
+				throw new Exception("Object translator parameter '$name' type must be class or interface but '$type' declared.");
+			}
+			$this->translators[$type->getName()] = $translator;
+		}
 		$this->sortTranslators = true;
 	}
 
diff --git a/tests/dibi/Connection.objectTranslator.phpt b/tests/dibi/Connection.objectTranslator.phpt
index 1664cd33..13255502 100644
--- a/tests/dibi/Connection.objectTranslator.phpt
+++ b/tests/dibi/Connection.objectTranslator.phpt
@@ -31,10 +31,7 @@ test('Without object translator', function () use ($conn) {
 
 
 test('Basics', function () use ($conn) {
-	$conn->setObjectTranslator(
-		Email::class,
-		fn(Email $email) => new Dibi\Expression('?', $email->address),
-	);
+	$conn->setObjectTranslator(fn(Email $email) => new Dibi\Expression('?', $email->address));
 	Assert::same(
 		reformat([
 			'sqlsrv' => "N'address@example.com'",
@@ -56,10 +53,7 @@ test('DateTime', function () use ($conn) {
 
 
 	// With object translator
-	$conn->setObjectTranslator(
-		Time::class,
-		fn(Time $time) => new Dibi\Expression('OwnTime(?)', $time->format('H:i:s')),
-	);
+	$conn->setObjectTranslator(fn(Time $time) => new Dibi\Expression('OwnTime(?)', $time->format('H:i:s')));
 	Assert::same(
 		reformat([
 			'sqlsrv' => "OwnTime(N'12:13:14')",
@@ -92,10 +86,7 @@ test('DateTime', function () use ($conn) {
 	);
 
 	// But DateTime translation can be overloaded
-	$conn->setObjectTranslator(
-		DateTimeInterface::class,
-		fn (DateTimeInterface $dt) => new Dibi\Expression('OwnDateTime'),
-	);
+	$conn->setObjectTranslator(fn(DateTimeInterface $dt) => new Dibi\Expression('OwnDateTime'));
 	Assert::same(
 		'OwnDateTime',
 		$conn->translate('?', $dt),
@@ -104,9 +95,9 @@ test('DateTime', function () use ($conn) {
 
 
 test('Complex structures', function () use ($conn) {
-	$conn->setObjectTranslator(Email::class, fn(Email $email) => new Dibi\Expression('?', $email->address));
-	$conn->setObjectTranslator(Time::class, fn (Time $time) => new Dibi\Expression('OwnTime(?)', $time->format('H:i:s')));
-	$conn->setObjectTranslator(DateTimeInterface::class, fn (DateTimeInterface $dt) => new Dibi\Expression('OwnDateTime'));
+	$conn->setObjectTranslator(fn(Email $email) => new Dibi\Expression('?', $email->address));
+	$conn->setObjectTranslator(fn(Time $time) => new Dibi\Expression('OwnTime(?)', $time->format('H:i:s')));
+	$conn->setObjectTranslator(fn(DateTimeInterface $dt) => new Dibi\Expression('OwnDateTime'));
 
 	$time = Time::createFromFormat('Y-m-d H:i:s', '2022-11-22 12:13:14');
 	Assert::same(
@@ -129,11 +120,27 @@ test('Complex structures', function () use ($conn) {
 
 
 test('Invalid translator', function () use ($conn) {
-	$conn->setObjectTranslator(
-		Email::class,
-		fn(Email $email) => 'foo',
+	Assert::exception(
+		fn() => $conn->setObjectTranslator(fn($email) => 'foo'),
+		Dibi\Exception::class, "Object translator parameter '\$email' must be declared with typehint.",
+	);
+
+	Assert::exception(
+		fn() => $conn->setObjectTranslator(fn(string $email) => 'foo'),
+		Dibi\Exception::class, "Object translator parameter '\$email' type must be class or interface but 'string' declared.",
+	);
+
+	Assert::exception(
+		fn() => $conn->setObjectTranslator(fn(Email|bool $email) => 'foo'),
+		Dibi\Exception::class, "Object translator parameter '\$email' type must be class or interface but 'bool' declared.",
+	);
+
+	Assert::exception(
+		fn() => $conn->setObjectTranslator(fn(Email|null $email) => 'foo'),
+		Dibi\Exception::class, "Object translator parameter '\$email' must not be nullable.",
 	);
 
+	$conn->setObjectTranslator(fn(Email $email) => 'foo');
 	Assert::exception(
 		fn() => $conn->translate('?', new Email),
 		Dibi\Exception::class, "Object translator for class 'Email' returned 'string' but Dibi\Expression expected.",