Barrier blocks and hitboxes don't appear when there's a slime block behind them

This is a world from about 14w05a, but I don't think that caused this problem. I'm in 14w07a, and when holding a barrier I should be able to see all barriers. However, this is not the case as when there's a slime block behind a barrier the barrier remains invisible wherever the slime block overlays it. And also connected to this glitch, any hitboxes don't appear when there's a slime block to overlay it as well. Thanks for reading 🙂