diff --git a/src/Spout/Writer/XLSX/Helper/FileSystemHelper.php b/src/Spout/Writer/XLSX/Helper/FileSystemHelper.php
index bf9e350..22d23e4 100644
--- a/src/Spout/Writer/XLSX/Helper/FileSystemHelper.php
+++ b/src/Spout/Writer/XLSX/Helper/FileSystemHelper.php
@@ -94,7 +94,7 @@ class FileSystemHelper extends \Box\Spout\Common\Helper\FileSystemHelper
      */
     protected function createRootFolder()
     {
-        $this->rootFolder = $this->createFolder($this->baseFolderPath, uniqid('xlsx'));
+        $this->rootFolder = $this->createFolder($this->baseFolderPath, uniqid('xlsx', true));
         return $this;
     }