diff --git a/mod/assign/submission/file/locallib.php b/mod/assign/submission/file/locallib.php
index 35c39f509a1..dcb4167412c 100644
--- a/mod/assign/submission/file/locallib.php
+++ b/mod/assign/submission/file/locallib.php
@@ -431,7 +431,7 @@ class assign_submission_file extends assign_submission_plugin {
         }
 
         foreach ($dir['subdirs'] as $subdir) {
-            $files = $this->format_submission_files($subdir);
+            $files = $this->flatten_list_of_files($subdir);
             $filessummary = array_merge($filessummary, $files);
         }