File Field does not overwrite when new file uploaded

Despite the text below a file field reading: "If you upload another file, the current file will be replaced.", if you upload an identical named file it will not be replaced. It will create a new file with _0, _1 ... _n appended. Though, the funny thing is, the old file will be deleted and the link stored is to the OLD file name. i.e. the one without _n on the end. So causing the link not to work and to instead take you to 'Access Denied'.

I've traced the issue to line 51 in file.inc.

Instead of:
if ($file = file_save_upload($fieldname, variable_get('file_directory_path', NULL))) {

You need to have:
if ($file = file_save_upload($fieldname, variable_get('file_directory_path', NULL), TRUE)) {

I don't know if this is correct. But it seems to work.

Thanks
Adam