Master Yi's Highlander doesn't give an additional 7 seconds buff if used again

With the new presence of mind master yi can finally have his ult buff longer than the cooldown of his ult. Problem is. If the buff is longer than 7 seconds when he uses ult the second time, he doesn't get any bonus even if the ult goes on cooldown.

If the bonus is lower than 7 seconds the buff refreshes to 7 seconds.

Expected: Buff longer/lower than 7 seconds + ult = add 7 seconds to current time

What actually happens: Buff longer than 7 seconds + ult = nothing Buff lower than 7 seconds + ult = refreshes to 7 seconds

If this is intended you shouldn't be able to ult if the buff is longer than 7 seconds, that's just a waste.