spaces in mailbox names

Howdy

I'm using mutt (1.5.17) on OSX. I'm having trouble with spaces in my
mailbox names. The trouble is that when I want to create a new mailbox
or change mailboxes with spaces I cannot type the space character.
When I want to open a mail box with a space in it I can usually tab
until I get all the matching mailboxes and select the one I want to
open. When I want to create a new mailbox I have to save it to
something and then rename it in the terminal. I've tried to escape the
spaces with a backslash, but that doesn't seem to work. Though
escaping them doesn't seem necessary because when I select mailboxes
using the tab method mentioned above mutt doesn't need to escape them.
Can someone help me here? How do I type a space in this field in mutt?