We were a mix of "RFC1234" and "RFC 1234". Apparently there is actually an answer for this, which is with a space textually and without a space in the citation/reference tag: https://datatracker.ietf.org/doc/html/rfc7322#section-3.5 Change-Id: I0c44023163fe3a2a3ffe28cbc644d4c952dc8f1e Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/48965 Reviewed-by: Adam Langley <agl@google.com>