Ship crew race always your main?

Hi,
I've taken over some planets of another race, and as it thrives in oxygen, while my people prefer hydrogen, I figured I'd let those planets build colonizers for the oxygen planets I want to colonize. However, I noticed that despite the enemy being the only race present on the planet, it will still crew any ship built with my main race, causing the colonized planets to be domed until I can send a freighter there to pick up the ex-crew.
Has anyone else noticed this oddity? Is it an intended feature, easily worked around, or actually an annoying bug?
Any thoughts, experience or comments appreciated.

Alien, Addict.