Can't place water on top a slab

Google my bug, found it resolved two years ago (MC-131021). But I still have it on 16.1.

What I expected to happen was...:
I wanted to place water on top of the slab (top position). I used shift-click. The result is the same with or without shift.

What actually happened was...:
Water placed inside the slab

Steps to Reproduce:
1. Place a slab in the air somewhere
2. Shift-click on it with the water bucket