--upload-tools doesn't work with bootstrap on armhf machine managed by maas

ubuntu@mw01-02:~$ juju --version
1.18.1-trusty-armhf

ubuntu@mw01-02:~$ uname -a
Linux mw01-02 3.13.0-24-generic-lpae #46-Ubuntu SMP Thu Apr 10 21:01:14 UTC 2014 armv7l armv7l armv7l GNU/Linux

ubuntu@mw01-02:~$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04 LTS"

ubuntu@mw01-02:~/juju$ juju bootstrap --constraints arch=armhf --upload-tools --debug
<....>
2014-05-06 11:07:49 DEBUG juju.environs.simplestreams simplestreams.go:985 metadata: &{map[com.ubuntu.cloud:server:12.04:amd64:{precise 12.04 amd64 map[20140408:0x114c2390 20140227:0x114c2780]} com.ubuntu.cloud:server:13.10:amd64:{saucy 13.10 amd64 map[20140227:0x114c2ab0 20140410:0x114c2cf0]} com.ubuntu.cloud:server:14.04:amd64:{trusty 14.04 amd64 map[20140416:0x114c2f60]}] map[crsn:map[euww1:map[region:eu-ams-1 endpoint:https://eu-ams-1.api.joyentcloud.com] ussw1:map[region:us-sw-1 endpoint:https://us-sw-1.api.joyentcloud.com] usww1:map[region:us-west-1 endpoint:https://us-west-1.api.joyentcloud.com] usee1:map[region:us-east-1 endpoint:https://us-east-1.api.joyentcloud.com]]] Thu, 17 Apr 2014 18:22:18 +0000 products:1.0 com.ubuntu.cloud:released:joyent}
2014-05-06 11:07:49 ERROR juju.cmd supercommand.go:300 environment "maas" of type maas does not support instances running on "armhf"

I can successfully use juju with this maas/armhf installation if I don't pass '--upload-tools' flag to bootstrap.
What I'm doing wrong?
Thanks