diff --git a/src/Forms/Container.php b/src/Forms/Container.php
index 858ddf5df..e0b176031 100644
--- a/src/Forms/Container.php
+++ b/src/Forms/Container.php
@@ -110,7 +110,7 @@ public function setValues($data, bool $erase = false)
 	 * @param  Control[]|null  $controls
 	 * @return object|array
 	 */
-	public function getValues($returnType = null, array $controls = null)
+	public function getValues($returnType = null, ?array $controls = null)
 	{
 		$form = $this->getForm(false);
 		if ($form && ($submitter = $form->isSubmitted())) {
@@ -137,7 +137,7 @@ public function getValues($returnType = null, array $controls = null)
 	 * @param  Control[]|null  $controls
 	 * @return object|array
 	 */
-	public function getUnsafeValues($returnType, array $controls = null)
+	public function getUnsafeValues($returnType, ?array $controls = null)
 	{
 		if (is_object($returnType)) {
 			$obj = $returnType;
@@ -217,7 +217,7 @@ public function isValid(): bool
 	 * Performs the server side validation.
 	 * @param  Control[]|null  $controls
 	 */
-	public function validate(array $controls = null): void
+	public function validate(?array $controls = null): void
 	{
 		$this->validated = null;
 		foreach ($controls ?? $this->getComponents() as $control) {
@@ -257,7 +257,7 @@ public function getErrors(): array
 
 
 	/** @return static */
-	public function setCurrentGroup(ControlGroup $group = null)
+	public function setCurrentGroup(?ControlGroup $group = null)
 	{
 		$this->currentGroup = $group;
 		return $this;
@@ -278,7 +278,7 @@ public function getCurrentGroup(): ?ControlGroup
 	 * @return static
 	 * @throws Nette\InvalidStateException
 	 */
-	public function addComponent(Nette\ComponentModel\IComponent $component, ?string $name, string $insertBefore = null)
+	public function addComponent(Nette\ComponentModel\IComponent $component, ?string $name, ?string $insertBefore = null)
 	{
 		parent::addComponent($component, $name, $insertBefore);
 		if ($this->currentGroup !== null) {
@@ -314,7 +314,7 @@ public function getForm(bool $throw = true): ?Form
 	 * Adds single-line text input control to the form.
 	 * @param  string|object  $label
 	 */
-	public function addText(string $name, $label = null, int $cols = null, int $maxLength = null): Controls\TextInput
+	public function addText(string $name, $label = null, ?int $cols = null, ?int $maxLength = null): Controls\TextInput
 	{
 		return $this[$name] = (new Controls\TextInput($label, $maxLength))
 			->setHtmlAttribute('size', $cols);
@@ -328,8 +328,8 @@ public function addText(string $name, $label = null, int $cols = null, int $maxL
 	public function addPassword(
 		string $name,
 		$label = null,
-		int $cols = null,
-		int $maxLength = null
+		?int $cols = null,
+		?int $maxLength = null
 	): Controls\TextInput {
 		return $this[$name] = (new Controls\TextInput($label, $maxLength))
 			->setHtmlAttribute('size', $cols)
@@ -341,7 +341,7 @@ public function addPassword(
 	 * Adds multi-line text input control to the form.
 	 * @param  string|object  $label
 	 */
-	public function addTextArea(string $name, $label = null, int $cols = null, int $rows = null): Controls\TextArea
+	public function addTextArea(string $name, $label = null, ?int $cols = null, ?int $rows = null): Controls\TextArea
 	{
 		return $this[$name] = (new Controls\TextArea($label))
 			->setHtmlAttribute('cols', $cols)->setHtmlAttribute('rows', $rows);
@@ -415,7 +415,7 @@ public function addCheckbox(string $name, $caption = null): Controls\Checkbox
 	 * Adds set of radio button controls to the form.
 	 * @param  string|object  $label
 	 */
-	public function addRadioList(string $name, $label = null, array $items = null): Controls\RadioList
+	public function addRadioList(string $name, $label = null, ?array $items = null): Controls\RadioList
 	{
 		return $this[$name] = new Controls\RadioList($label, $items);
 	}
@@ -425,7 +425,7 @@ public function addRadioList(string $name, $label = null, array $items = null):
 	 * Adds set of checkbox controls to the form.
 	 * @param  string|object  $label
 	 */
-	public function addCheckboxList(string $name, $label = null, array $items = null): Controls\CheckboxList
+	public function addCheckboxList(string $name, $label = null, ?array $items = null): Controls\CheckboxList
 	{
 		return $this[$name] = new Controls\CheckboxList($label, $items);
 	}
@@ -435,7 +435,7 @@ public function addCheckboxList(string $name, $label = null, array $items = null
 	 * Adds select box control that allows single item selection.
 	 * @param  string|object  $label
 	 */
-	public function addSelect(string $name, $label = null, array $items = null, int $size = null): Controls\SelectBox
+	public function addSelect(string $name, $label = null, ?array $items = null, ?int $size = null): Controls\SelectBox
 	{
 		return $this[$name] = (new Controls\SelectBox($label, $items))
 			->setHtmlAttribute('size', $size > 1 ? $size : null);
@@ -449,8 +449,8 @@ public function addSelect(string $name, $label = null, array $items = null, int
 	public function addMultiSelect(
 		string $name,
 		$label = null,
-		array $items = null,
-		int $size = null
+		?array $items = null,
+		?int $size = null
 	): Controls\MultiSelectBox {
 		return $this[$name] = (new Controls\MultiSelectBox($label, $items))
 			->setHtmlAttribute('size', $size > 1 ? $size : null);
@@ -482,7 +482,7 @@ public function addButton(string $name, $caption = null): Controls\Button
 	 * @param  string  $src  URI of the image
 	 * @param  string  $alt  alternate text for the image
 	 */
-	public function addImageButton(string $name, string $src = null, string $alt = null): Controls\ImageButton
+	public function addImageButton(string $name, ?string $src = null, ?string $alt = null): Controls\ImageButton
 	{
 		return $this[$name] = new Controls\ImageButton($src, $alt);
 	}
diff --git a/src/Forms/Controls/BaseControl.php b/src/Forms/Controls/BaseControl.php
index 7a7f9a3d4..41defb7fa 100644
--- a/src/Forms/Controls/BaseControl.php
+++ b/src/Forms/Controls/BaseControl.php
@@ -134,7 +134,7 @@ public function loadHttpData(): void
 	 * Loads HTTP data.
 	 * @return mixed
 	 */
-	protected function getHttpData($type, string $htmlTail = null)
+	protected function getHttpData($type, ?string $htmlTail = null)
 	{
 		return $this->getForm()->getHttpData($type, $this->getHtmlName() . $htmlTail);
 	}
diff --git a/src/Forms/Controls/CheckboxList.php b/src/Forms/Controls/CheckboxList.php
index c933ca26c..dd058db80 100644
--- a/src/Forms/Controls/CheckboxList.php
+++ b/src/Forms/Controls/CheckboxList.php
@@ -35,7 +35,7 @@ class CheckboxList extends MultiChoiceControl
 	/**
 	 * @param  string|object  $label
 	 */
-	public function __construct($label = null, array $items = null)
+	public function __construct($label = null, ?array $items = null)
 	{
 		parent::__construct($label, $items);
 		$this->control->type = 'checkbox';
diff --git a/src/Forms/Controls/ChoiceControl.php b/src/Forms/Controls/ChoiceControl.php
index 6e890f0e3..c9b652f39 100644
--- a/src/Forms/Controls/ChoiceControl.php
+++ b/src/Forms/Controls/ChoiceControl.php
@@ -27,7 +27,7 @@ abstract class ChoiceControl extends BaseControl
 	private $items = [];
 
 
-	public function __construct($label = null, array $items = null)
+	public function __construct($label = null, ?array $items = null)
 	{
 		parent::__construct($label);
 		if ($items !== null) {
diff --git a/src/Forms/Controls/CsrfProtection.php b/src/Forms/Controls/CsrfProtection.php
index a2db72c9a..1c4bf2ac5 100644
--- a/src/Forms/Controls/CsrfProtection.php
+++ b/src/Forms/Controls/CsrfProtection.php
@@ -81,7 +81,7 @@ public function getToken(): string
 	}
 
 
-	private function generateToken(string $random = null): string
+	private function generateToken(?string $random = null): string
 	{
 		if ($random === null) {
 			$random = Nette\Utils\Random::generate(10);
diff --git a/src/Forms/Controls/ImageButton.php b/src/Forms/Controls/ImageButton.php
index d326e9c18..035fcbe0b 100644
--- a/src/Forms/Controls/ImageButton.php
+++ b/src/Forms/Controls/ImageButton.php
@@ -19,7 +19,7 @@ class ImageButton extends SubmitButton
 	 * @param  string  $src  URI of the image
 	 * @param  string  $alt  alternate text for the image
 	 */
-	public function __construct(string $src = null, string $alt = null)
+	public function __construct(?string $src = null, ?string $alt = null)
 	{
 		parent::__construct();
 		$this->control->type = 'image';
diff --git a/src/Forms/Controls/MultiChoiceControl.php b/src/Forms/Controls/MultiChoiceControl.php
index 5a223d026..2d0d71878 100644
--- a/src/Forms/Controls/MultiChoiceControl.php
+++ b/src/Forms/Controls/MultiChoiceControl.php
@@ -27,7 +27,7 @@ abstract class MultiChoiceControl extends BaseControl
 	private $items = [];
 
 
-	public function __construct($label = null, array $items = null)
+	public function __construct($label = null, ?array $items = null)
 	{
 		parent::__construct($label);
 		if ($items !== null) {
diff --git a/src/Forms/Controls/MultiSelectBox.php b/src/Forms/Controls/MultiSelectBox.php
index 5bcfc64bc..c154de1f4 100644
--- a/src/Forms/Controls/MultiSelectBox.php
+++ b/src/Forms/Controls/MultiSelectBox.php
@@ -24,7 +24,7 @@ class MultiSelectBox extends MultiChoiceControl
 	private $optionAttributes = [];
 
 
-	public function __construct($label = null, array $items = null)
+	public function __construct($label = null, ?array $items = null)
 	{
 		parent::__construct($label, $items);
 		$this->setOption('type', 'select');
diff --git a/src/Forms/Controls/RadioList.php b/src/Forms/Controls/RadioList.php
index 233f40ae1..5a9282b0b 100644
--- a/src/Forms/Controls/RadioList.php
+++ b/src/Forms/Controls/RadioList.php
@@ -38,7 +38,7 @@ class RadioList extends ChoiceControl
 	/**
 	 * @param  string|object  $label
 	 */
-	public function __construct($label = null, array $items = null)
+	public function __construct($label = null, ?array $items = null)
 	{
 		parent::__construct($label, $items);
 		$this->control->type = 'radio';
diff --git a/src/Forms/Controls/SelectBox.php b/src/Forms/Controls/SelectBox.php
index a33c9ac28..8d69f6e38 100644
--- a/src/Forms/Controls/SelectBox.php
+++ b/src/Forms/Controls/SelectBox.php
@@ -30,7 +30,7 @@ class SelectBox extends ChoiceControl
 	private $optionAttributes = [];
 
 
-	public function __construct($label = null, array $items = null)
+	public function __construct($label = null, ?array $items = null)
 	{
 		parent::__construct($label, $items);
 		$this->setOption('type', 'select');
diff --git a/src/Forms/Controls/TextInput.php b/src/Forms/Controls/TextInput.php
index e497e6b9f..78696f490 100644
--- a/src/Forms/Controls/TextInput.php
+++ b/src/Forms/Controls/TextInput.php
@@ -21,7 +21,7 @@ class TextInput extends TextBase
 	/**
 	 * @param  string|object  $label
 	 */
-	public function __construct($label = null, int $maxLength = null)
+	public function __construct($label = null, ?int $maxLength = null)
 	{
 		parent::__construct($label);
 		$this->control->maxlength = $maxLength;
diff --git a/src/Forms/Form.php b/src/Forms/Form.php
index 45587a9cf..070e486b3 100644
--- a/src/Forms/Form.php
+++ b/src/Forms/Form.php
@@ -131,7 +131,7 @@ class Form extends Container implements Nette\HtmlStringable
 	private $beforeRenderCalled;
 
 
-	public function __construct(string $name = null)
+	public function __construct(?string $name = null)
 	{
 		if ($name !== null) {
 			$this->getElementPrototype()->id = 'frm-' . $name;
@@ -235,7 +235,7 @@ public function allowCrossOrigin(): void
 	/**
 	 * Cross-Site Request Forgery (CSRF) form protection.
 	 */
-	public function addProtection(string $errorMessage = null): Controls\CsrfProtection
+	public function addProtection(?string $errorMessage = null): Controls\CsrfProtection
 	{
 		$control = new Controls\CsrfProtection($errorMessage);
 		$this->addComponent($control, self::PROTECTOR_ID, key((array) $this->getComponents()));
@@ -382,7 +382,7 @@ public function setSubmittedBy(?SubmitterControl $by)
 	 * Returns submitted HTTP data.
 	 * @return mixed
 	 */
-	public function getHttpData(int $type = null, string $htmlName = null)
+	public function getHttpData(?int $type = null, ?string $htmlName = null)
 	{
 		if ($this->httpData === null) {
 			if (!$this->isAnchored()) {
@@ -514,7 +514,7 @@ protected function receiveHttpData(): ?array
 	/********************* validation ****************d*g**/
 
 
-	public function validate(array $controls = null): void
+	public function validate(?array $controls = null): void
 	{
 		$this->cleanErrors();
 		if ($controls === null && $this->submittedBy instanceof SubmitterControl) {
diff --git a/src/Forms/Helpers.php b/src/Forms/Helpers.php
index a1c899b18..59c42e9cf 100644
--- a/src/Forms/Helpers.php
+++ b/src/Forms/Helpers.php
@@ -160,8 +160,8 @@ public static function exportRules(Rules $rules): array
 
 	public static function createInputList(
 		array $items,
-		array $inputAttrs = null,
-		array $labelAttrs = null,
+		?array $inputAttrs = null,
+		?array $labelAttrs = null,
 		$wrapper = null
 	): string {
 		[$inputAttrs, $inputTag] = self::prepareAttrs($inputAttrs, 'input');
@@ -193,7 +193,7 @@ public static function createInputList(
 	}
 
 
-	public static function createSelectBox(array $items, array $optionAttrs = null, $selected = null): Html
+	public static function createSelectBox(array $items, ?array $optionAttrs = null, $selected = null): Html
 	{
 		if ($selected !== null) {
 			$optionAttrs['selected?'] = $selected;
diff --git a/src/Forms/Rendering/DataClassGenerator.php b/src/Forms/Rendering/DataClassGenerator.php
index fdb6358d4..0c56a63eb 100644
--- a/src/Forms/Rendering/DataClassGenerator.php
+++ b/src/Forms/Rendering/DataClassGenerator.php
@@ -29,7 +29,7 @@ final class DataClassGenerator
 	public $useSmartObject = true;
 
 
-	public function generateCode(Form $form, string $baseName = null): string
+	public function generateCode(Form $form, ?string $baseName = null): string
 	{
 		$baseName = $baseName ?? preg_replace('~Form$~', '', ucwords((string) $form->getName()));
 		return $this->processContainer($form, $baseName);
diff --git a/src/Forms/Rendering/DefaultFormRenderer.php b/src/Forms/Rendering/DefaultFormRenderer.php
index 6be8ea4cd..8ee515106 100644
--- a/src/Forms/Rendering/DefaultFormRenderer.php
+++ b/src/Forms/Rendering/DefaultFormRenderer.php
@@ -129,7 +129,7 @@ class DefaultFormRenderer implements Nette\Forms\FormRenderer
 	 * Provides complete form rendering.
 	 * @param  string  $mode  'begin', 'errors', 'ownerrors', 'body', 'end' or empty to render all
 	 */
-	public function render(Nette\Forms\Form $form, string $mode = null): string
+	public function render(Nette\Forms\Form $form, ?string $mode = null): string
 	{
 		if ($this->form !== $form) {
 			$this->form = $form;
@@ -220,7 +220,7 @@ public function renderEnd(): string
 	/**
 	 * Renders validation errors (per form or per control).
 	 */
-	public function renderErrors(Nette\Forms\Control $control = null, bool $own = true): string
+	public function renderErrors(?Nette\Forms\Control $control = null, bool $own = true): string
 	{
 		$errors = $control
 			? $control->getErrors()
diff --git a/src/Forms/Rules.php b/src/Forms/Rules.php
index bee4ae63b..f41bbbb66 100644
--- a/src/Forms/Rules.php
+++ b/src/Forms/Rules.php
@@ -221,7 +221,7 @@ public function getToggles(bool $actual = false): array
 
 
 	/** @internal */
-	public function getToggleStates(array $toggles = [], bool $success = true, bool $emptyOptional = null): array
+	public function getToggleStates(array $toggles = [], bool $success = true, ?bool $emptyOptional = null): array
 	{
 		foreach ($this->toggles as $id => $hide) {
 			$toggles[$id] = ($success xor !$hide) || !empty($toggles[$id]);
@@ -247,7 +247,7 @@ public function getToggleStates(array $toggles = [], bool $success = true, bool
 	/**
 	 * Validates against ruleset.
 	 */
-	public function validate(bool $emptyOptional = null): bool
+	public function validate(?bool $emptyOptional = null): bool
 	{
 		$emptyOptional = $emptyOptional ?? (!$this->isRequired() && !$this->control->isFilled());
 		foreach ($this as $rule) {
diff --git a/tests/bootstrap.php b/tests/bootstrap.php
index 039552af1..abb911275 100644
--- a/tests/bootstrap.php
+++ b/tests/bootstrap.php
@@ -15,7 +15,7 @@
 date_default_timezone_set('Europe/Prague');
 
 
-function before(Closure $function = null)
+function before(?Closure $function = null)
 {
 	static $val;
 	if (!func_num_args()) {