Chunks random regeneration

What I expected to happen was:
I select my survival world in 1.5 to play it and nothing is changed

What actually happened was:
A chunk regenerated, deleting a huge part of my house

Steps to Reproduce:
1. Join your world
2. A chunk will regenerated, deleting part of your construction.

When I first started playing this world in 1.2.3, the lake was not present.