I'm not understanding your case much. Proto3 does not serialize zeros/false, precisely because it'd be a waste without a benefit. After deserialization, the value is as equal to zero as if the zero had been written on the wire or on disk. Why would you want to store that?

Is nullability of primitive types what you're missing? As in, having a boolean value that can be true, false, or null. If you need that, defining your field as google.protobuf.BoolValue instead of bool gives you that (same with the other primitive types: https://github.com/google/protobuf/blob/master/src/google/pr... ). But making primitive types never null aligns proto3 with most programming languages, making the generated code more idiomatic and performant.