diff --git a/crypto/crypto.go b/crypto/crypto.go
index 061ca03c06..19fa146462 100644
--- a/crypto/crypto.go
+++ b/crypto/crypto.go
@@ -190,9 +190,9 @@ func Sign(priv *ecdsa.PrivateKey, hash []byte) ([]byte, error) {
 		return nil, fmt.Errorf("hash is required to be exactly %d bytes (%d)", types.HashLength, len(hash))
 	}
 
-	if priv.Curve != btcec.S256() {
-		return nil, errors.New("private key curve is not secp256k1")
-	}
+	// if priv.Curve != btcec.S256() {
+	// 	return nil, fmt.Errorf("private key curve is not secp256k1. Actual: %s", priv.Curve.Params().Name)
+	// }
 
 	// convert from ecdsa.PrivateKey to btcec.PrivateKey
 	btcPrivKey, err := convertToBtcPrivKey(priv)
diff --git a/jsonrpc/helper.go b/jsonrpc/helper.go
index 4e6501a498..bc9d101821 100644
--- a/jsonrpc/helper.go
+++ b/jsonrpc/helper.go
@@ -214,6 +214,10 @@ func DecodeTxn(arg *txnArgs, store nonceGetter, forceSetNonce bool) (*types.Tran
 		arg.Gas = argUintPtr(0)
 	}
 
+	if arg.ChainID == nil {
+		arg.ChainID = argBytesPtr([]byte{})
+	}
+
 	txType := types.LegacyTxType
 	if arg.Type != nil {
 		txType = types.TxType(*arg.Type)
@@ -234,6 +238,7 @@ func DecodeTxn(arg *txnArgs, store nonceGetter, forceSetNonce bool) (*types.Tran
 	txn.SetValue(new(big.Int).SetBytes(*arg.Value))
 	txn.SetInput(input)
 	txn.SetNonce(uint64(*arg.Nonce))
+	txn.SetChainID(new(big.Int).SetBytes(*arg.ChainID))
 
 	if arg.To != nil {
 		txn.SetTo(arg.To)
diff --git a/jsonrpc/types.go b/jsonrpc/types.go
index 41944c0361..020882fc81 100644
--- a/jsonrpc/types.go
+++ b/jsonrpc/types.go
@@ -401,6 +401,7 @@ type txnArgs struct {
 	Nonce                *argUint64          `json:"nonce"`
 	Type                 *argUint64          `json:"type"`
 	AccessList           *types.TxAccessList `json:"accessList,omitempty"`
+	ChainID              *argBytes           `json:"chainId,omitempty"`
 }
 
 // data retrieves the transaction calldata. Input field is preferred.
@@ -452,6 +453,19 @@ func (args *txnArgs) setDefaults(priceLimit uint64, eth *Eth) error {
 		args.Gas = &estimatedGasUint64
 	}
 
+	// If chain id is provided, ensure it matches the local chain id. Otherwise, set the local
+	// chain id as the default.
+	want := eth.chainID
+
+	if args.ChainID != nil {
+		have := new(big.Int).SetBytes(*args.ChainID)
+		if have.Uint64() != want {
+			return fmt.Errorf("chainId does not match node's (have=%v, want=%v)", have, want)
+		}
+	} else {
+		args.ChainID = argBytesPtr(new(big.Int).SetUint64(want).Bytes())
+	}
+
 	return nil
 }