Cannot test manual deploys with wily

Passing the series wily to deploy_stack is not enough to provision wily instances:
    deploy_job.py --series wily manual extracted-bin/usr/lib/juju-1.26-alpha1/bin/juju ./artifacts manual-deploy-wily-amd64

We see precise was selected
machines:
  "0":
    agent-state: started
    agent-version: 1.26-alpha1
    dns-name: ec2-52-22-29-89.compute-1.amazonaws.com
    instance-id: 'manual:'
    series: precise
    hardware: arch=amd64 cpu-cores=1 mem=7450M
    state-server-member-status: has-vote
  "1":
    agent-state: started
    agent-version: 1.26-alpha1
    dns-name: ec2-52-21-48-113.compute-1.amazonaws.com
    instance-id: manual:ec2-52-21-48-113.compute-1.amazonaws.com
    series: precise
    hardware: arch=amd64 cpu-cores=1 mem=7450M
  "2":
    agent-state: pending
    agent-version: 1.26-alpha1
    dns-name: ec2-52-20-178-65.compute-1.amazonaws.com
    instance-id: manual:ec2-52-20-178-65.compute-1.amazonaws.com
    series: precise
    hardware: arch=amd64 cpu-cores=1 mem=7450M