bzr index AssertionError: Somehow we ended up with too much compressed data

It seems that to run bzr search, I need to create a search index. So in my repo I ran

 bzr index .

It ran for a while, saying stuff like Indexing...:Indexing texts: commits 2/4.B
But then it gave me a traceback, as attached. The bottom line was:

....
  File "/usr/lib/python2.7/dist-packages/bzrlib/chunk_writer.py", line 144, in finish
    % (self.bytes_out_len, self.chunk_size))
AssertionError: Somehow we ended up with too much compressed data, 4032 > 3976

It happens every time I run bzr index . in this repository, but indexing works in a different repo.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: bzr 2.5.1-0ubuntu2
ProcVersionSignature: Ubuntu 3.13.0-41.70~precise1-generic 3.13.11.11
Uname: Linux 3.13.0-41-generic x86_64
ApportVersion: 2.0.1-0ubuntu17.8
Architecture: amd64
Date: Sun Nov 30 11:27:52 2014
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
MarkForUpload: True
PackageArchitecture: all
ProcEnviron:
 TERM=screen
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: bzr
UpgradeStatus: No upgrade log present (probably fresh install)