diff --git a/lua/oil/config.lua b/lua/oil/config.lua
index b5cb6f6f..5e06cb16 100644
--- a/lua/oil/config.lua
+++ b/lua/oil/config.lua
@@ -417,8 +417,8 @@ M.setup = function(opts)
     new_conf.confirmation = vim.tbl_deep_extend("keep", opts.preview, default_config.confirmation)
   end
 
-  M.new_file_mode = tonumber(tostring(opts.new_file_mode), 8)
-  M.new_folder_mode = tonumber(tostring(opts.new_folder_mode), 8)
+  new_conf.new_file_mode = tonumber(tostring(new_conf.new_file_mode), 8)
+  new_conf.new_folder_mode = tonumber(tostring(new_conf.new_folder_mode), 8)
   -- Backwards compatibility. We renamed the 'preview' config to 'preview_win'
   if opts.preview and opts.preview.update_on_cursor_moved ~= nil then
     new_conf.preview_win.update_on_cursor_moved = opts.preview.update_on_cursor_moved