Very little shadowing on Leaves in 'Fast' mode + smooth lighting off (less than 1.7.4)

Leaves in 'Fast' mode with smooth lighting off has less shadowing than in 1.7.4. Shown in attached screenshots.

What I expected to happen was...:
The shadowing would be the same as 1.7.4 (I know about problems in 14w06a that were fixed in 14w06b. This bug affects 14w06b.)

What actually happened was...:
There was less shadowing in 14w06b than in 1.7.4.

Steps to Reproduce:
1. Set graphics to 'fast' and smooth lighting off.
2. Place down down some leaves in both 14w06b and 1.7.4.
3. Less shadowing in 14w06b.

EDIT: also affects 14w32a.