Accessing Unity 5 Environmental Lighting Skybox from C# script

I’m trying to rotate a cube map skybox at runtime. Since the ‘Skybox/Cubemap’ shader already exposes a ‘Rotation’ uniform, I thought I could just write a script along the lines of:

public class Clouds : MonoBehaviour {
	int step = 1;

	void FixedUpdate () {
		step += 1;
		step %= 360;
		Material skybox = RenderSettings.skybox;
		skybox.SetInt ("Rotation", step);
	}
}

The idea being that it should be like manually moving the ‘Rotation’ slider for the cubemap shader from the inspector. But when doing it thru the code above, the parameter doesn’t seem to update. Any thoughts on what am I doing wrong?

Material skybox = RenderSettings.skybox;
skybox.SetInt (“Rotation”, step);
RenderSettings.skybox = skybox;

step += 1;
step %= 360;
Material skybox = RenderSettings.skybox;
skybox.SetInt (“_Rotation”, step);

“Rotation” = " _Rotation"