Duplicity fails to back up to directories with spaces in B2

If I try to back up to a B2 key that contains a space (b2://user@bucket/Purchased Apps), only the initial backup is successful. Subsequent backups fail with a HTTP 505. If I remove the space, I can run an incremental backup. Since B2 doesn't support server-side renames, I used rclone to copy the backup repository into a new directory, and a backup worked fine after that.

I'm using duplicity 0.7.14 on Ubuntu 16.04 from the PPA.

/usr/bin/duplicity --name duply_purchased-apps --encrypt-key XXX --encrypt-key XXX --sign-key XXX --verbosity 9 --exclude-filelist /etc/duply/purchased-apps/exclude '/main/media/Purchased Apps' 'b2://XXX@XXXX/Purchased Apps'

<snip>

Registering (mktemp) temporary file /tmp/duplicity-x6csjM-tempdir/mktemp-2jFn1G-2
Getting file duplicity-full.20170913T000217Z.manifest.gpg
Getting https://f001.backblazeb2.com/file/XXX/Purchased Apps/duplicity-full.2
0170913T000217Z.manifest.gpg
Backtrace of previous error: Traceback (innermost last):
  File "/usr/lib/python2.7/dist-packages/duplicity/backend.py", line 369, in inner_retry
    return fn(self, *args)
  File "/usr/lib/python2.7/dist-packages/duplicity/backend.py", line 545, in get
    self.backend._get(remote_filename, local_path)
  File "/usr/lib/python2.7/dist-packages/duplicity/backends/b2backend.py", line 105, in _get
    resp = self.get_or_post(url, None)
  File "/usr/lib/python2.7/dist-packages/duplicity/backends/b2backend.py", line 296, in get_or_post
    raise e
 HTTPError: HTTP Error 505: HTTP Version Not Supported

Attempt 1 failed. HTTPError: HTTP Error 505: HTTP Version Not Supported