Beacon is not rendered good when is sorrounded by blocks.

I was on a Creative Server and I started to make lamps... and then... I noticed that the Beacon's Sides are not shown when they are blocks arround...
As you can see... Im using Faithful 32x32 (Probably a Texture Bug), but then I used the Default texture and it happens too... Please, can you fix this?

How to Reproduce:
1.- Make sure that you are in a Creative Multiplayer Server. (Dont know if it can be reproduced in Singleplayer)
2.- Place a Beacon.
3.- Place blocks arround making sure that it covers the 4 sides.
4.- Watch te Bug.