Grindstones are rendered too dark when blocks are placed adjacent to them while smooth lighting is enabled

The Bug:

Grindstones are rendered too dark when blocks are placed adjacent to them while smooth lighting is enabled.

Steps to Reproduce:

1. Enable smooth lighting and place down a sideways-facing grindstone.
2. Place blocks all around the grindstone.
3. Take note as to whether or not grindstones are rendered too dark when blocks are placed adjacent to them while smooth lighting is enabled.

Observed Behavior:

Grindstones are rendered too dark.

Expected Behavior:

Grindstones would not be rendered too dark.