Historical balance requests with block identifiers from before account was created

Hey Rosetta team,

I’m working on adding support for historical balance requests in Mina’s Rosetta implementation and need clarification on a certain nuance.

If an /account/balance request is made for account_identifier A with block_identifier B but account A was created later than the block referenced by B, should we return a balance of 0 or an error?

Thanks,
Omer