diff --git a/src/Hostname.php b/src/Hostname.php
index a97d787d1..4ae2cb227 100644
--- a/src/Hostname.php
+++ b/src/Hostname.php
@@ -1761,6 +1761,7 @@ class Hostname extends AbstractValidator
             33 => '/^[\x{002d}0-9א-ת]{1,63}$/iu'],
         'PR'  => [1 => '/^[\x{002d}0-9a-záéíóúñäëïüöâêîôûàèùæçœãõ]{1,63}$/iu'],
         'PT'  => [1 => '/^[\x{002d}0-9a-záàâãçéêíóôõú]{1,63}$/iu'],
+        'RS'  => [1 => '/^[\x{002d}0-9a-zßáâäçéëíîóôöúüýăąćčďđęěĺľłńňőŕřśşšţťůűźżž]{1,63}$/iu'],
         'RU'  => [1 => '/^[\x{002d}0-9а-яё]{1,63}$/iu'],
         'SA'  => [1 => '/^[\x{002d}.0-9\x{0621}-\x{063A}\x{0641}-\x{064A}\x{0660}-\x{0669}]{1,63}$/iu'],
         'SE'  => [1 => '/^[\x{002d}0-9a-zäåéöü]{1,63}$/iu'],