diff --git a/composer.json b/composer.json
index 7c8b54d..fbb1566 100644
--- a/composer.json
+++ b/composer.json
@@ -46,6 +46,9 @@
             "src/AtolOnline/Traits/",
             "src/AtolOnline/Constants/",
             "tests/"
+        ],
+        "files": [
+            "src/helpers.php"
         ]
     }
 }
diff --git a/src/helpers.php b/src/helpers.php
new file mode 100644
index 0000000..c4f0900
--- /dev/null
+++ b/src/helpers.php
@@ -0,0 +1,16 @@
+<?php
+
+if (!function_exists('valid_strlen')) {
+    /**
+     * Возвращает корректную длину строки
+     *
+     * @param string $value
+     * @return int
+     */
+    function valid_strlen(string $value): int
+    {
+        return function_exists('mb_strlen')
+            ? mb_strlen($value)
+            : strlen($value);
+    }
+}