Chickens suffocate when spawning

I know that animal suffocation was fixed in the 1.4.1 pre-release but discovered this today. I was spawning chickens in a small enclosure as shown in the screenshot. When the eggs hit the back wall, around about where the dirt meets the stone, about 50% spawned in the dirt and suffocated immediately. All chickens spawned in at that point suffered some damage, but I put this down to the fact that they were spawned at the wall and not on the floor. I was spawning the chickens one at a time (i.e. not spamming the back wall) as I didn't want to hit newly spawned chickens with eggs immediately after they appeared.

Steps to reproduce:

Aim eggs at line between dirt and stone at back wall of enclosure, or just above line. Approx 50% of chickens that spawn will do so in the dirt block as if having landed on the stone block's top.

Expected result:

Chicken spawns normally.

Not a major bug, just flagging it as out of 6 or so chickens that spawned, at least half died.

Cheers!!!

T