How to sign commits in existing PR?


I’ve created a PR with unsigned commits, but the repo rules have changed and now it requires all commits to be signed. What I see on the PR page after approval is the following:

Merging is blocked

The base branch requires all commits to be signed. Learn more about signing commits.

I’ve set up signing key and now can sign my commits, but what would be correct actions regarding this particular PR? One option I see is to close it and create a new one with commits signed, but that doesn’t seem the best way of solving the problem. Other options available?