How to properly use options "subConfigurations" with subpackage "vibe-d:core"?

When I write in dub.json "subConfigurations": {"vibe-d": "win32"} and run dub build I receive messages

<...>
vibe-d:data 0.7.27: target for configuration "library" is up to date.
vibe-d:core 0.7.27: target for configuration "libevent" is up to date.
<...>
vibe-d 0.7.27: building configuration "win32"...

and I get dependency on libevent.

I tried to change "subConfigurations": {"vibe-d:core": "win32"}, {"vibe-d": "win32", "vibe-d:core": "win32"}, etc. But I still get dependency on libevent.

How to build "win32" configuration?