Hostile mobs spawning in light >7 at bedrock level.

Prior to 1.5 mobs were not spawning in my mines where all blocks have a light level of 8+. Since the update mobs are now spawning in these mines. The behavior is similar to void fog reducing light levels in Alpha 1.2. I have found 3 hostile mobs (2 creepers, 1 skeleton) in ~ 1.5 hours of gameplay.