Problem with underscore-to-dash conversion when using linked containers

[McSlow]

The puppet module turns some underscores in container names into dashes - which is ok ... but
this causes trouble when linking containers:

Mär 07 21:02:25 localhost.localdomain docker[8864]: docker: Error response from daemon: Could not get container for my_mysql.

(note the undercore...)

Seems that the linked containers' underscores are not converted to dashes and docker therefore cannot find them...

test case:

#Set up a stupid Wordpress instance...

#https://github.com/garethr/garethr-docker
include 'docker'

#images

#https://hub.docker.com/_/wordpress/
docker::image{'wordpress':}
#https://hub.docker.com/_/mysql/
docker::image{'mysql':}

#containers
docker::run {'my_mysql':
  image => 'mysql',
  env => ['MYSQL_ROOT_PASSWORD=wordpress'],
}
docker::run { 'my_wordpress':
  image   => 'wordpress',
  links  => ['my_mysql:mysql'],
  ports  => ['8080:80'],
  expose => ['80'],
  depends => ['my_mysql'],
}

(just :%s/my_/my/g to make it work....)

Here's the unit file:

# This file is managed by Puppet and local changes
# may be overwritten

[Unit]
Description=Daemon for my_wordpress
After=docker.service docker-my-mysql.service
Wants=
Requires=docker.service docker-my-mysql.service

[Service]
Restart=on-failure
StartLimitInterval=20
StartLimitBurst=5
TimeoutStartSec=0
Environment="HOME=/root"
ExecStartPre=-/usr/bin/docker kill my-wordpress
ExecStartPre=-/usr/bin/docker rm  my-wordpress
ExecStart=/usr/bin/docker run \
        --net bridge -m 0b --expose=80 --link my_mysql:mysql -p 8080:80  \# my-mysql!
        --name my-wordpress \
        wordpress \

ExecStop=-/usr/bin/docker kill my-wordpress
ExecStop=-/usr/bin/docker rm  my-wordpress

[Install]
WantedBy=multi-user.target

regards,
Björn