Cycles Smoke Rendering Causes Compositing Issues

I created a simple smoke simulation and rendered it in Cycles. It all worked out great, until I tried to use the Map Value node in compositing to create a mist effect in the background, and I got this, where it’s using the domain cube as the smoke object instead of the smoke shape itself. Is it possible to fix this?

Not with the current functionality in Blender, no.

Okay; thanks for responding. I’ve found a workaround for now.