[Client] Promoted during an unranked draft game

I duo queue'd with an unranked friend, in a draft normal Summoner's rift game. Before the game I was 2 wins, 2 losses in my promos to platinum. After game I got a message that I won my series, and that I was promoted to plat 5. I'm pretty sure this is not the intended behaviour.

Let me know if I can supply any more detail.

So quick repro steps:

1. get Gold 1. Get to Platinum promos. Lose one game, win one, lose another, win one. (so you're 2wins, 2 losses)
2. Start a draft pick normal game. Invite an unranked player.
3. Win a game.
4. Congratulations. You have been promoted to Plat 5.

This is clearly not the correct behaviour, as the game wasn't ranked in the first place.