Lighting bug involving slabs, sides appear darker.

When creating e.g. a roof using slabs and full blocks (shown below), lighting is not properly applied to the slabs, making their sides appear significantly darker than in unaffected areas.
While the affected roof was lit from below, I was only able to recreate this bug without a light source underneath. The slabs and full blocks must be arranged in a pyramid-like shape, the inside of which is not being exposed to any light.