glass shader not working with normal map in cycles 1.-I am making some low poly objects with normal maps in cycles. All of them are working correctly but when I plug a normal map in a object with a glass shader it becomes opaque with some reflections on the surface.
Is there an additional step to make normal maps work with a glass shader?

2.-I discover something weird. The fact is that I am using a tangent space normal map(purple map), but if I change the setting in the normal node from tangent to object space(blue and yellow map) it seems to work fine.

I uploaded a zip folder with the blend file and the normal map here:
https://copy.com/ADi3bvAGpR9o
I SOLVED IT !!! I did another object and again I ran into the same problem. But this time the mesh looked fine from above but completely black from below. I switched from object space to tangent space and after a few hours I decided to play around with the normal map strength and it seems that glass shader doesn´t like normal map values greater than 0.4 and After 0.46 the mesh starts looking completely black.

this values are for my particular project.