Fence gate and horizontal fence posts not rendering bottom face.

Fence gate and horizontal fence posts not rendering bottom face.

What I expected to happen was...:
The fence gate/fence rendering normally.

What actually happened was...:
The bottom face doesn't render, and you can see through it.

Steps to Reproduce:
1. Place down a fence gate/fence.
2. Dig out a few blocks so that you can see under it.