diff --git a/src/Forms/ControlGroup.php b/src/Forms/ControlGroup.php
index 740949a5..174bb960 100644
--- a/src/Forms/ControlGroup.php
+++ b/src/Forms/ControlGroup.php
@@ -15,7 +15,7 @@
 /**
  * A user group of form controls.
  */
-class ControlGroup
+final class ControlGroup
 {
 	protected \SplObjectStorage $controls;
 	private array $options = [];
diff --git a/src/Forms/Helpers.php b/src/Forms/Helpers.php
index d3c2ae1c..6d1a1317 100644
--- a/src/Forms/Helpers.php
+++ b/src/Forms/Helpers.php
@@ -18,7 +18,7 @@
 /**
  * Forms helpers.
  */
-class Helpers
+final class Helpers
 {
 	use Nette\StaticClass;
 
diff --git a/src/Forms/Rule.php b/src/Forms/Rule.php
index 27d57815..95811939 100644
--- a/src/Forms/Rule.php
+++ b/src/Forms/Rule.php
@@ -16,7 +16,7 @@
 /**
  * Single validation rule or condition represented as value object.
  */
-class Rule
+final class Rule
 {
 	public Control $control;
 	public mixed $validator;
diff --git a/src/Forms/Rules.php b/src/Forms/Rules.php
index 1db83c43..5b670e8d 100644
--- a/src/Forms/Rules.php
+++ b/src/Forms/Rules.php
@@ -17,7 +17,7 @@
  * List of validation & condition rules.
  * @implements \IteratorAggregate<int, Rule>
  */
-class Rules implements \IteratorAggregate
+final class Rules implements \IteratorAggregate
 {
 	private const NegRules = [
 		Form::Filled => Form::Blank,
diff --git a/src/Forms/Validator.php b/src/Forms/Validator.php
index d38f9a6c..bf3656bf 100644
--- a/src/Forms/Validator.php
+++ b/src/Forms/Validator.php
@@ -17,7 +17,7 @@
 /**
  * Common validators.
  */
-class Validator
+final class Validator
 {
 	use Nette\StaticClass;