Probably not a good idea as shellac has wax in it.

De-waxed shellac, such as Sealcoat, would work. It has a slight amber-ness to it.

Thanks! I didn't realize shellac had wax in it. I think I'll play it safe and just use the poly. It's slightly amber anyways, an extra coat would probably give me a similar look without the risk of the coats not bonding.

Just use de-waxed shellac if you're worried.

I've done this many, many times though and have had no failures over 30+ years of using oil based poly over shellac made up from Behlen flakes. I do sand between the shellac application and the poly, fwiw.

yes I agree with the last post . Shellac is the best primer , it actually works as a barrier coat between coats to prevent a bad reaction with the previous product . Lightly sand with 320 grit paper or green scotch bright pad , and paint away !