How to fix iMessage preview problem with ios11?

Before the ios11 update, whenever someone texted me, my messages showed as “iMessage” in my lock screen and home screen so when I wanted to view them without the person knowing, I would swipe down and it would reveal the message. However, after the ios11 update, it no longer does that. Sure it still says “iMessage” in the lock screen, but when i’m in my phone, after i’ve put in my password, it shows the actual message in the banners now and that is not what I want. Is there anyway i could fix this?