deis BUILDPACK_URL issue

gistfile1.sh

$ deis config:list
=== web01 Config
BUILDPACK_URL      https://github.com/heroku/heroku-buildpack-php

$ deis config:set BUILDPACK_URL=https://github.com/heroku/heroku-buildpack-php                                                                   
Creating config... done, v14

=== web01
DEIS_APP: web01
DEIS_RELEASE: v14
BUILDPACK_URL: https://github.com/heroku/heroku-buildpack-php

$ git commit -am "deis" --allow-empty
[master 42d846c] deis

$ git push deis master
Counting objects: 1, done.
Writing objects: 100% (1/1), 184 bytes | 0 bytes/s, done.
Total 1 (delta 0), reused 0 (delta 0)
-----> Node.js app detected
       
       PRO TIP: Specify a node version in package.json
       See https://devcenter.heroku.com/articles/nodejs-support
       
-----> Defaulting to latest stable node: 0.10.32
-----> Downloading and installing node
-----> Installing dependencies
       [removed npm output that I expected to fail because I don't use node/npm on the server, just on local]
To ssh://git@deis.example.com:2222/web01.git
   e826f83..42d846c  master -> master

On line 20 I'm expecting to see "Fetching custom build pack", not "Node.js app detected"