diff --git a/helper/upload.php b/helper/upload.php
index f7a54ef..d29886a 100644
--- a/helper/upload.php
+++ b/helper/upload.php
@@ -1,7 +1,7 @@
 <?php
   require_once('uuid.php');
 
-  function fileextension ($fname) {
+  function fileextension (string $fname): string {
     $ext = strrpos($fname, '.');
 
     return $ext === false ? '' : substr($fname, $ext + 1);