NSEC_PER_SEC is an unresolved identifier on Linux?

I'm running into this error on Linux in code which works on macOS:

/swift/Tests/WitnessTests/WitnessTests.swift:81:101: error: use of unresolved identifier 'NSEC_PER_SEC'

Is this because I need to import something, or is this not available on Linux?

NSEC_PER_SEC is defined in Dispatch, are you importing it? If you are, then this looks like a bug.

Yeah I am importing it. Ok thanks for the info, I will file a bug report