[backportpackage] doesn't work if package isn't already in Ubuntu

I tried using backportpackage for a new package and the upload was rejected because backportpackage did not include the original source.

$ backportpackage --suffix= -s unstable -u ppa:jbicha/dev libmusicbrainz5
backportpackage: Downloading libmusicbrainz5_5.0.1.orig.tar.gz from ftp.debian.org (0.104 MiB)
backportpackage: Downloading libmusicbrainz5_5.0.1-1.diff.gz from ftp.debian.org (0.003 MiB)
dpkg-source: info: extracting libmusicbrainz5 in libmusicbrainz5-quantal
dpkg-source: info: unpacking libmusicbrainz5_5.0.1.orig.tar.gz
dpkg-source: info: applying libmusicbrainz5_5.0.1-1.diff.gz
dch warning: new version (5.0.1-1~ubuntu12.10.1) is less than
the current version number (5.0.1-1).
 dpkg-buildpackage -rfakeroot -d -us -uc -S -nc -sd
dpkg-buildpackage: source package libmusicbrainz5
dpkg-buildpackage: source version 5.0.1-1~ubuntu12.10.1
dpkg-buildpackage: source changed by Jeremy Bicha <***@ubuntu.com>
 dpkg-source --before-build libmusicbrainz5-quantal
dpkg-buildpackage: warning: it is a bad idea to generate a source package without cleaning up first, it might contain undesired files.
 dpkg-source -b libmusicbrainz5-quantal
dpkg-source: warning: Version number suggests Ubuntu changes, but there is no XSBC-Original-Maintainer field
dpkg-source: warning: source directory 'libmusicbrainz5-quantal' is not <sourcepackage>-<upstreamversion> 'libmusicbrainz5-5.0.1'
dpkg-source: warning: .orig directory name libmusicbrainz5-quantal.orig is not <package>-<upstreamversion> (wanted libmusicbrainz5-5.0.1.orig)
dpkg-source: info: using source format `1.0'
dpkg-source: info: building libmusicbrainz5 using existing libmusicbrainz5_5.0.1.orig.tar.gz
dpkg-source: info: building libmusicbrainz5 in libmusicbrainz5_5.0.1-1~ubuntu12.10.1.diff.gz
dpkg-source: info: building libmusicbrainz5 in libmusicbrainz5_5.0.1-1~ubuntu12.10.1.dsc
 dpkg-genchanges -S -sd >../libmusicbrainz5_5.0.1-1~ubuntu12.10.1_source.changes
dpkg-genchanges: warning: the current version (5.0.1-1~ubuntu12.10.1) is earlier than the previous one (5.0.1-1)
dpkg-genchanges: not including original source code in upload
 dpkg-source --after-build libmusicbrainz5-quantal
dpkg-buildpackage: source only, diff-only upload (original source NOT included)
 signfile libmusicbrainz5_5.0.1-1~ubuntu12.10.1.dsc Jeremy Bicha <***@ubuntu.com>

You need a passphrase to unlock the secret key for
user: "Jeremy Bicha <email address hidden>"
4096-bit RSA key, ID EBFE6C7D, created 2011-04-28

 signfile libmusicbrainz5_5.0.1-1~ubuntu12.10.1_source.changes Jeremy Bicha <***@ubuntu.com>

You need a passphrase to unlock the secret key for
user: "Jeremy Bicha <***@***>"
4096-bit RSA key, ID EBFE6C7D, created 2011-04-28

Successfully signed dsc and changes files
Please check libmusicbrainz5 5.0.1-1~ubuntu12.10.1 in file:///tmp/backportpackage-DtiFDu carefully!
Do you want to upload the package to ppa:jbicha/dev [Y|n]? y
Checking signature on .changes
gpg: Signature made Sat 02 Jun 2012 01:10:04 PM EDT using RSA key ID EBFE6C7D
gpg: Good signature from "Jeremy Bicha <***@***>"
gpg: aka "Jeremy Bicha <***@ubuntu.com>"
Good signature on /tmp/backportpackage-DtiFDu/libmusicbrainz5_5.0.1-1~ubuntu12.10.1_source.changes.
Checking signature on .dsc
gpg: Signature made Sat 02 Jun 2012 01:10:04 PM EDT using RSA key ID EBFE6C7D
gpg: Good signature from "Jeremy Bicha <***@***>"
gpg: aka "Jeremy Bicha <***@ubuntu.com>"
Good signature on /tmp/backportpackage-DtiFDu/libmusicbrainz5_5.0.1-1~ubuntu12.10.1.dsc.
Uploading to ppa (via sftp to ppa.launchpad.net):
  libmusicbrainz5_5.0.1-1~ubuntu12.10.1.dsc: done.
  libmusicbrainz5_5.0.1-1~ubuntu12.10.1.diff.gz: done.
  libmusicbrainz5_5.0.1-1~ubuntu12.10.1_source.changes: done.
Successfully uploaded packages.

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: ubuntu-dev-tools 0.142
ProcVersionSignature: Ubuntu 3.4.0-3.8-generic 3.4.0
Uname: Linux 3.4.0-3-generic x86_64
ApportVersion: 2.1.1-0ubuntu2
Architecture: amd64
CheckboxSubmission: 201084ed41ea7548f8becd47fa4d1e6c
CheckboxSystem: c541d13ea4f205f2fd751f76ed21105b
Date: Sat Jun 2 14:32:15 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
PackageArchitecture: all
SourcePackage: ubuntu-dev-tools
UpgradeStatus: No upgrade log present (probably fresh install)