MacOS – brew bundle reporting “Error: unknown command: bundle”

I'm completely puzzled by this one. I have refactored my install scripts to use the new brew bundle feature. However, I'm getting "Error: unknown command: bundle"

$ which brew
/usr/local/bin/brew

$ brew -v
Homebrew 0.9.5

$ brew doctor
Please note that these warnings are just used to help the Homebrew maintainers
with debugging if you file an issue. If everything you use Homebrew for is
working fine: please don't worry and just ignore them. Thanks!

Warning: You have a curlrc file
If you have trouble downloading packages with Homebrew, then maybe this
is the problem? If the following command doesn't work, then try removing
your curlrc:
  curl http://github.com

$ brew update
Already up-to-date.

$ cat ~/.dotfiles/install/brewfile-basic
# Important early installs

install hub # https://hub.github.com
install git-extras # https://github.com/visionmedia/git-extras
install bash-completion # http://bash-completion.alioth.debian.org

# Cleaning up Brew caches

linkapps
cleanup
prune

$ brew bundle ~/.dotfiles/install/brewfile-basic
Error: Unknown command: bundle

$ brew bundle
Error: Unknown command: bundle

In all other ways, brew is working.

Any ideas? Is this feature not in the current build?

— Christopher Allen