When you are making sheep follow you with wheat, they will not be able to jump up blocks

when you usually make sheep follow you, they will be able to jump up a block, but with snapshot 14w31 minecraft, when sheep follow you and come to a block, they will try to jump on it over and over but simply not be able to.

here are the steps to reproduce this:
1. get some wheat
2. find a sheep and make it follow you
3. come to a 1 block high "wall" and the sheep will not be able to jump over it