Straight Alpha Missing Error

Hi, I'm new in chroma on DaVinci, I need to export my chroma in straight alpha mode but that didn't work so I tried to interpretate my footage as alpha straight in the clip attributes but there is no stright mode. Only None and Premultiplied, am I missing something?

PD. When I tried to export the alpha in straight mode it brings back the removed background, this doesn't happen in premultiplied but I need my footage in straight mode.

[Peter Chamberlain]

moved to Resolve forum

What is "chroma" in your case? And what format are you writing to? Not all formats are meant for storing straight alpha (although you can in all of them), so it might be simply removed from options based on this.