How to properly render smoke on a transparent background? When rendering volumes with Film > Transparent enabled, the alpha appears to be the wrong type (premultiplied/straight).
In the 3D view it works as expected:



This is a known bug.

Is there any way to work around this?
It's a viewer issue only. Try compositing over a gray background using the alpha-over node. 
If the result is correct, then your file output (without the gray background, of course) will be correct as long as you store it as EXR or any other format with associated (premultiplied) alpha channel, as it's the only way to store pixels that are both transparent and emissive (which is what fire is).
The resulting EXR will be fine to be composited over any background, and fire should look ok.