// First push the multisig dummy, note that due to BIP147 (NULLDUMMY) it must be a zero-length element.
htlc_tx.input[0].witness.push(Vec::new());
htlc_tx.input[0].witness.push(counterparty_signature.serialize_der().to_vec());
htlc_tx.input[0].witness.push(signature.serialize_der().to_vec());
// First push the multisig dummy, note that due to BIP147 (NULLDUMMY) it must be a zero-length element.
htlc_tx.input[0].witness.push(Vec::new());
htlc_tx.input[0].witness.push(counterparty_signature.serialize_der().to_vec());
htlc_tx.input[0].witness.push(signature.serialize_der().to_vec());