Link to attachment filename with two consecutive whitespaces is broken by WYSIWYG editor

Attached a file with filename "RE: VST and TOC.msg". The file was automatically renamed to remove the colon - i.e. on the Attachments screen the name shows up as "RE VST and TOC.msg", however on mouseover of the filename link the URL shows up at the bottom of the browser as "RE++VST+and+TOC.msg". i.e. two white spaces between "RE" and "VST".
Page has a link pointing to the Attachment. Entering Wiki Markup Edit mode for the page is fine and the link has two spaces in the appropriate place, however if WYSIWIG mode is selected the two consecutive white spaces are converted to a single white space. Returning to Wiki Markup mode shows that the space is still missing. If page is saved at this point, without manually re-entering the second space, the link to the attachment is broken and highlighted red.