Image Upload via HTTP rejected, Missing Signature Key

I have a private registry on a closed network, and I need to push an image to it via the HTTP api. It works fine for signed images (like the ones found on Docker Hub), but if the manifest is missing a Signatures section (in the case of some internally developed images that reside on another private registry), the manifest Put call at the end of the upload fails, and the logs for the registry say “Err: Invalid Manifest, Detail: Missing signature key”.

It looks to me like the ‘signatures’ section of the Manifest is optional based on the schema here and that images without signatures will just be flagged as unsigned when client try to pull them. Is there some setting for the registry I should be changing?