"Peer's Certificate issuer is not recognized" on git push with r/w deploy key

Summary

We are using a deploy key with write access for our Jenkins server so we can tag builds in GitLab properly. On "git push --tags ..." we get the error message "Peer's Certificate issuer is not recognized."

Is this a feature or bug?

Steps to reproduce

This setup is running on RHEL 7 with latest GitLab and Jenkins versions.

1. Set up GitLab and Jenkins servers.
2. Generate an SSH key pair for Jenkins user
3. Add Jenkins public key as deploy key to GitLab project, checking the write access checkbox.
4. Run Jenkins build job containing "git push" at the end.

Build fails with above error message.

Expected behavior

We expected the build to complete and the tag to show up.

Actual behavior

Build terminates with above error message.

Results of GitLab application Check

All self-checks complete successfully.