diff --git a/src/Api/KktMonitor.php b/src/Api/KktMonitor.php
index 037af92..1e63643 100644
--- a/src/Api/KktMonitor.php
+++ b/src/Api/KktMonitor.php
@@ -56,8 +56,8 @@ class KktMonitor extends AtolClient
     protected function fetchAll(?int $limit = null, ?int $offset = null): KktResponse
     {
         $params = [];
-        $limit && $params['limit'] = $limit;
-        $offset && $params['offset'] = $offset;
+        !is_null($limit) && $params['limit'] = $limit;
+        !is_null($offset) && $params['offset'] = $offset;
         return $this->sendRequest('GET', self::getUrlToMethod('cash-registers'), $params);
     }
 
diff --git a/src/Enum.php b/src/Enum.php
new file mode 100644
index 0000000..cfa866a
--- /dev/null
+++ b/src/Enum.php
@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace AtolOnline;
+
+use AtolOnline\Exceptions\InvalidEnumValueException;
+
+/**
+ * Расширение класса перечисления
+ */
+class Enum extends \MyCLabs\Enum\Enum
+{
+    /**
+     * @inheritDoc
+     * @throws InvalidEnumValueException
+     */
+    public static function isValid($value)
+    {
+        return parent::isValid($value)
+            ?: throw new InvalidEnumValueException(static::class, $value);
+    }
+}