Affects Version/s: Minecraft 1.9 Pre-Release 2
Fix Version/s: None
What I expected to happen was... the stairs to be at the light level surrounding them.
What actually happened was... part of the stairs register with a light level of zero, allowing mobs to spawn.
Steps to Reproduce
1. Put down stairs
2. With the f3 screen on, shiftwalk up the stars.
3. Keep an eye out for where "Light: 0"