SerializeObject with zod SafeParseReturnType

[spring prawn]

I'm running into a types issue with Zod where my fetcher is supposed to return this type:

field: string;
result: z.SafeParseReturnType<SchemaInput, SchemaOutput>;

I understand that it must be serialised, that's not my problem. My problem is I get an "Unsafe assignment of an any value." error due to the following issue: Property 'success' does not exist on type 'SerializeObject<UndefinedToOptional<SafeParseSuccess<SchemaOutput>>>'
I don't know why the success boolean is not available after being serialised, I suspect that this is a bug. The type is being set in the useFetcher generic:

useFetcher<{
  field: string;
  result: z.SafeParseReturnType<SchemaInput, SchemaOutput>;
}>();

Does anyone know why this might be happening?
Zod 3.21.4
Remix 1.15.0

[spring prawn]

After some playing around in TypeScript playground, I can see that the success variable is being removed by the serialise stuff:
https://www.typescriptlang.org/play?#code/JYWwDg9gTgLgBAbzgZQKZWAQwDbAF6oBiUEIcAvnAGYlkBEAAlKiMAB4C0UArgHYD0vCABNUdANwAoUJFiI8lGqTh08IiZMkBjCLwDO8PVoAWLTHAC8cPADoIAIwBWqLTAAUCSXG9x+-OAB6APySAJBmwNgAgsLCzHp6AFzWNgYYvADmbgCUNhHYOQA0YWCYCQDu0MLJtmnAmUWS5NlSkjAAnmCocAAqqAaWKciYVKgACphQeqgASqgw3FC8PZ2oADy29WDcMBs2yCZmAHyFKRA727u2B6YgmEdHUn4+gSEdXb39MABMg2gYOHwRFoaz6BiOkmePmCbVWnwMAGZBtcRuNJtNkNwtFp+no9ucYJc1u9UBAqHAjLd7o9If5oW84WCYAAWZH7VETKaoACiUBIUD2Wx2xNWZIphzuDyedO8MJJ8JgAFY-ugsLgCMRSKCvgiIVDZQyPkyAGwqgHq4FapnMvUy15AA