Problem compositer if a world texture is applied ? How I can do ?

Hi !

I have a world paper sky texture in my scene.
I have a cube on my first layer.
And another one in my second that emit light.

I want to use compositer to add some effect to the second layer. But I have a problem. My world texture is rendered with each layer. So I can made a traitment only on my lamp and apply it and then mix this effect with the first layer and then have only one time my world background texture.

If I use this texture is because I want to affect the light in the scene with the color of this texture in indirect ligthing…

How can I resolve my problem of compositing in my case ?

Sorry… I find ! Deselect sky in Layer render panel…