diff --git a/files/delete.me b/files/delete.me
index 18beddaa8..69e3582f0 100644
--- a/files/delete.me
+++ b/files/delete.me
@@ -1 +1,10 @@
-default directory for uploaded files
\ No newline at end of file
+default directory for uploaded files
+
+## The `markdownized_previews` subdirectory
+
+Redmine may create a `markdownized_previews` subdirectory in this
+directory to store cached Markdown previews generated from supported
+Microsoft Office and LibreOffice attachments.
+
+You can safely delete these cached files. They will be automatically
+regenerated when needed.