The live-build version I used was 3.0~a37-1 from deb http://live.debian.net/ wheezy-snapshots main contrib non-free which was listed at the bottom of http://live.debian.net/devel/live-build/ I didn't want to build from source. The hook specified in http://lists.debian.org/debian-live/2011/11/msg00075.html appears to have been executed and the ISO generated works as expected. Thanks!