I had some problem like this using protobuf2 enums The way protobuf handles enums, it recommends having an "UNKNOWN" as value 0, as when deserializing from the

I had some problem like this using protobuf2 enums The way protobuf handles enums, it recommends having an "UNKNOWN" as value 0, as when deserializing from the wire any unknown enum value gets turned into value 0. So it's recommended to have something like enum FailReason { UNKNOWN_ERROR = 0, ERROR_1 = 1, ERROR_2 = 2, etc } But someone long ago made the enum I was dealing with look like this enum { SUCCESS = 0, ERROR_1 = 1, ERROR_2 = 2, etc. } But this means I can't easily add a new error case, as it'll get interpreted as a success unless I carefully roll out the change to the receiving servers first. But if I wasn't dealing with a distributed system I would like to have exhaustive checking.