Mobs do not spawn at the heights 16, 32, 48, 64, 80... (Multiples of 16)

Hostile Mobs will not spawn at certain heights if the darkness they would spawn in is caused by the night. So if the skylight is 0 mobs WILL spawn at these heights.

The heights are:
16, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176, 192, 208, 224, 240
(basicly every 16*n)

I guess this is due to the fact that Chunks are split up vertically in parts with the height of 16. So the problem occurs if a mob spawns inside one part, but the block it spawns on is inside the part below.

How to reproduce:

1. Singleplayer
2. Create new World
3. Gamemode: Creative
4. More World Options...
5. World Type: Superflat
6. Customize
7. Presets
8. paste the following preset into the box at the top: 3;64*minecraft:stone;1;
9. Use Preset
10. Done
11. Create new World
12. set the time to night (/time set 18000)

No mobs will spawn!
You can use the preset 3;63*minecraft:stone;1; or 3;65*minecraft:stone;1; instead and they will spawn.