from a project with zmqd as a dependency, with an empty ~/.dub

1st run:

$ dub build
The following changes will be performed:
Fetch zeromq ~master, userWide
Fetch zmqd ~master, userWide
Fetching zeromq ~master...
Placing zeromq ~master to /home/space/phujfj/.dub/packages/...
Fetching zmqd ~master...
Placing zmqd ~master to /home/space/phujfj/.dub/packages/...
Error executing command build: Unknown dependency: zeromq

then 2nd attempt:

$ dub build
The following changes will be performed:
Fetch zeromq ~master, userWide
Fetching zeromq ~master...
Placing zeromq ~master to /home/space/phujfj/.dub/packages/...
Error executing command build: zeromq (~master) needs to be removed from '/home/space/phujfj/.dub/packages/zeromq-master' prior placement.

What gives?