Sheep armour

I was derping off in creative mode and decided to spash a sheep with a 6 minute splash potion of invisability and the only thing that I could see was the sheeps wool
I don't know if this will help but I was on a 1.4.2 server

What I expected to happen was the sheep to dissapear compleatly

What actually happened was the sheep had it's wool showing

Steps to Reproduce:
1. Get a 6 minute spash potion from the creative mode
2. Find naturaly spawned sheep and splash it with the potion
3. Notice that the sheep has it's wool showing