Mesos_release not taken into account when building a custom box

[afraisse]

While having the following config.json :
{ "platform": "virtualbox", "mesos_release": "0.24.1-0.2.35.ubuntu1404", "box_name": "playa_mesos_ubuntu_14.04_201601041324", "base_url": "http://downloads.mesosphere.io/playa-mesos", "ip_address": "10.141.141.10", "vm_ram": "4096", "vm_cpus": "4" }
The box created after running bin/build has the newest version of mesos installed (mesos-master --version returns 0.28.0).