How did I (Nunu & Willimp) get vision on baron?

I know the second time I got it because of the GP ult, but how did I get it for the first few seconds? I mean, im not complaining, since I was able to steal it, but I have been looking at the replay for like an hour now and am so confused on what gave me the little bit of vision on him... Do attacks from the baron grant vision on him?
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