diff --git a/main/document/download_uploaded_files.php b/main/document/download_uploaded_files.php
index 97ae7810fd..d826ef2f97 100644
--- a/main/document/download_uploaded_files.php
+++ b/main/document/download_uploaded_files.php
@@ -16,7 +16,7 @@ $courseInfo = api_get_course_info($courseCode);
 if (empty($courseInfo)) {
     $courseInfo = api_get_course_info();
 }
-$type = preg_replace("/[^a-zA-Z]+/", '', $type);
+$type = preg_replace("/[^a-zA-Z_]+/", '', $type);
 
 if (empty($courseInfo) || empty($type) || empty($file)) {
     api_not_allowed(true);