diff --git a/plugin/maxdown.vim b/plugin/maxdown.vim
index 1951f1f..efb84d9 100644
--- a/plugin/maxdown.vim
+++ b/plugin/maxdown.vim
@@ -68,6 +68,7 @@ function! s:preview() abort
   let source = expand('%:p')
   let dest = expand('~/.maxdown.preview.html')
   call s:invoke(dest, source, bufnr('%'))
+  call setfperm(dest, 'rw-------')
   call s:show(dest, expand('%:t'))
 endfunction