How to write a Formula that uses keg-only bison for build

I’m trying to write a formula for a library that requires a Bison version newer than that provided by macOS to build. (macOS has Bison 2.3, and I need Bison 2.6).

When I add depends_on "bison" => :build to my Formula, it builds, but brew audit --new-formula says

Dependency 'bison' is provided by macOS; please replace 'depends_on' with 'uses_from_macos'.

But if I use uses_from_macos "bison" => :build, my Formula fails to build from source because the macOS Bison is too old.

What’s the right way to handle this?

Thanks,
Brian

Just depends_on and comment that the macOS version is too old.