Phone vibrates for incoming messages even if the conversation is open

After the latest app update, my notifications for Whatsapp are all screwed up.

What I had: phone vibrates when receiving a message when Whatsapp is closed.

What I have now: phone vibrates for incoming messages even when I have the conversation open.

I can't find how to turn it off without turning off vibration completely. Any ideas?

Edit: I'm on Iphone.