Perma Blue Buff

So, I was playing Zyra in my last game. At some point, while in my passive, I killed the Zed who had Blue Buff.

I respawned with the buff, timer, mana regen, cdr and all. I was a little intrigued, but I figured it might have been a change due to the last patch, so I didn't care much.

I started being a tad weirded out when I realised that about five minutes after acquiring the blue buff, I still had the visual icon around me, without the effect. In fact, i've had it on me until the end of the game.

Nothing gamebreaking (afaik!), just really annoying.