Old villagers corrupting chunks

If you have villagers in 1.7 or before, and then load that same world with 1.8, the villagers will corrupt the chunks

Steps to Reproduce:
1. create 1.7 (or before) world
2. Find villagers and do some trading
3. Update that world to 1.8
4. place blocks near villagers and reload world.
5.blocks will be gone due to corrupted villagers corrupting the chunks in that world