FX/Flare is always on top

Hello everybody. I need your help. I've got 2 objects in my scene: a basic terrain, and a cube with the shader FX/Flare. My problem is this: when the object is positioned below the terrain (Y=-1), its visible anyway. I tried to change the Render Queue of the shader but i couldn't find any value that corrects this behaviour. If possible, I don't want to pick another shader, I like the effect of this one... but I think i need to tweak it a little. I don't know how.