diff --git a/src/Forms/Validator.php b/src/Forms/Validator.php
index 11b838267..1d76848da 100644
--- a/src/Forms/Validator.php
+++ b/src/Forms/Validator.php
@@ -131,18 +131,23 @@ public static function validateStatic(IControl $control, bool $arg): bool
 	/**
 	 * Is control filled?
 	 */
-	public static function validateFilled(Controls\BaseControl $control): bool
+	public static function validateFilled(IControl $control): bool
 	{
-		return $control->isFilled();
+		if ($control instanceof Controls\BaseControl || method_exists($control, 'isFilled')) {
+			return $control->isFilled();
+		}
+
+		$value = $control->getValue();
+		return $value !== null && $value !== [] && $value !== '';
 	}
 
 
 	/**
 	 * Is control not filled?
 	 */
-	public static function validateBlank(Controls\BaseControl $control): bool
+	public static function validateBlank(IControl $control): bool
 	{
-		return !$control->isFilled();
+		return !static::validateFilled($control);
 	}
 
 
@@ -318,9 +323,10 @@ public static function validateFloat(IControl $control): bool
 	/**
 	 * Is file size in limit?
 	 */
-	public static function validateFileSize(Controls\UploadControl $control, $limit): bool
+	public static function validateFileSize(IControl $control, $limit): bool
 	{
 		foreach (static::toArray($control->getValue()) as $file) {
+			Validators::assert($file, Nette\Http\FileUpload::class, 'control value');
 			if ($file->getSize() > $limit || $file->getError() === UPLOAD_ERR_INI_SIZE) {
 				return false;
 			}
@@ -333,10 +339,11 @@ public static function validateFileSize(Controls\UploadControl $control, $limit)
 	 * Has file specified mime type?
 	 * @param  string|string[]  $mimeType
 	 */
-	public static function validateMimeType(Controls\UploadControl $control, $mimeType): bool
+	public static function validateMimeType(IControl $control, $mimeType): bool
 	{
 		$mimeTypes = is_array($mimeType) ? $mimeType : explode(',', $mimeType);
 		foreach (static::toArray($control->getValue()) as $file) {
+			Validators::assert($file, Nette\Http\FileUpload::class, 'control value');
 			$type = strtolower($file->getContentType());
 			if (!in_array($type, $mimeTypes, true) && !in_array(preg_replace('#/.*#', '/*', $type), $mimeTypes, true)) {
 				return false;
@@ -349,9 +356,10 @@ public static function validateMimeType(Controls\UploadControl $control, $mimeTy
 	/**
 	 * Is file image?
 	 */
-	public static function validateImage(Controls\UploadControl $control): bool
+	public static function validateImage(IControl $control): bool
 	{
 		foreach (static::toArray($control->getValue()) as $file) {
+			Validators::assert($file, Nette\Http\FileUpload::class, 'control value');
 			if (!$file->isImage()) {
 				return false;
 			}
diff --git a/tests/Forms/Validator.customControl.phpt b/tests/Forms/Validator.customControl.phpt
new file mode 100644
index 000000000..1325095c1
--- /dev/null
+++ b/tests/Forms/Validator.customControl.phpt
@@ -0,0 +1,122 @@
+<?php
+
+/**
+ * Test: Nette\Forms\Controls\BaseControl
+ */
+
+declare(strict_types=1);
+
+use Nette\Forms\Form;
+use Nette\Forms\Validator;
+use Nette\Http\FileUpload;
+use Nette\Utils\AssertionException;
+use Tester\Assert;
+
+
+require __DIR__ . '/../bootstrap.php';
+
+
+class CustomControl implements \Nette\Forms\IControl
+{
+
+	private $value;
+
+
+	public function __construct($value)
+	{
+		$this->value = $value;
+	}
+
+
+	public function setValue($value)
+	{
+		$this->value = $value;
+	}
+
+
+	public function getValue()
+	{
+		return $this->value;
+	}
+
+
+	public function validate(): void
+	{
+	}
+
+
+	public function getErrors(): array
+	{
+		return [];
+	}
+
+
+	public function isOmitted(): bool
+	{
+		return false;
+	}
+
+}
+
+
+test(function () { // filled, blank
+	$input = new CustomControl('');
+	Assert::false(Validator::validateFilled($input));
+	Assert::true(Validator::validateBlank($input));
+
+	$input = new CustomControl(null);
+	Assert::false(Validator::validateFilled($input));
+	Assert::true(Validator::validateBlank($input));
+
+	$input = new CustomControl([]);
+	Assert::false(Validator::validateFilled($input));
+	Assert::true(Validator::validateBlank($input));
+
+	$input = new CustomControl(42);
+	Assert::true(Validator::validateFilled($input));
+	Assert::false(Validator::validateBlank($input));
+});
+
+
+test(function () { // file upload related validators
+	$input = new CustomControl(new FileUpload([
+		'name' => 'foo',
+		'size' => 1,
+		'tmp_name' => __FILE__,
+		'error' => UPLOAD_ERR_OK
+	]));
+	Assert::true(Validator::validateFileSize($input, 42));
+	Assert::true(Validator::validateMimeType($input, ['text/x-php']));
+	Assert::false(Validator::validateImage($input));
+
+	$input = new CustomControl(new FileUpload([
+		'name' => 'foo',
+		'size' => 100,
+		'tmp_name' => __DIR__ . '/files/logo.gif',
+		'error' => UPLOAD_ERR_OK
+	]));
+	Assert::false(Validator::validateFileSize($input, 42));
+	Assert::false(Validator::validateMimeType($input, ['text/x-php']));
+	Assert::true(Validator::validateImage($input));
+
+	Assert::exception(
+		function () : void {
+			Assert::false(Validator::validateFileSize(new CustomControl('foo'), 42));
+		},
+		AssertionException::class
+	);
+
+	Assert::exception(
+		function () : void {
+			Assert::false(Validator::validateMimeType(new CustomControl('foo'), ['plain/text']));
+		},
+		AssertionException::class
+	);
+
+	Assert::exception(
+		function () : void {
+			Assert::false(Validator::validateImage(new CustomControl('foo')));
+		},
+		AssertionException::class
+	);
+});