+ character is not converted to space in attachment filename when downloading file to disk

If I attach a file called "été et hiver.txt" on a wiki page, then download the file to disk I get a file called "été+et+hiver.txt". It would be better to either leave the spaces alone in the attachment file name (although I don't know what the consequences could be) or convert the + character back to a space in the Content Disposition header so that the user gets the same file name as they had before.