diff --git a/lib/Widget/Validator/File.php b/lib/Widget/Validator/File.php
index <HASH>..<HASH> 100644
--- a/lib/Widget/Validator/File.php
+++ b/lib/Widget/Validator/File.php
@@ -433,7 +433,7 @@ class File extends AbstractValidator
             $file = basename($this->originFile);

             // Use substr instead of pathinfo, because pathinfo may return error value in unicode

             if (false !== $pos = strrpos($file, '.')) {

-                $this->ext = substr($file, $pos + 1);

+                $this->ext = strtolower(substr($file, $pos + 1));

             } else {

                 $this->ext = '';

             }
fixed file extension is case insensitive in file validtor and upload widget, close #<I>