In AWS Lex is the fallback intent fulfilled or failed?

Question

I'm implementing a lambda to accept dialog and fulfillment calls from a lex bot. The purpose of the lambda is to be a passthrough - accept utterance, confidence score, and session data, log it, and return control back to lex, which returns control back to AWS Connect.

On most intents this can be done by implementing the validation dialog hook and returning delegate. For the fallback intent, only the fulfillment response is available as a hook.

Which is the correct response to minimally interact with the default fallback intent behavior? Is it returning Fulfilled:

const CLOSE_FULFILLED = {
    dialogAction: {
        type: "Close",
        fulfillmentState: "Fulfilled"
    }
}

or Failed:

const CLOSE_FAILED = {
    dialogAction: {
        type: "Close",
        fulfillmentState: "Failed"
    }
}