diff --git a/rpc/api.go b/rpc/api.go
index 0596aee48..20b586686 100644
--- a/rpc/api.go
+++ b/rpc/api.go
@@ -48,16 +48,6 @@ func (p *EthereumApi) Transact(args *NewTxArgs, reply *interface{}) (err error)
 		return err
 	}
 
-	// TODO: align default values to have the same type, e.g. not depend on
-	// common.Value conversions later on
-	if args.Gas.Cmp(big.NewInt(0)) == 0 {
-		args.Gas = p.xeth().DefaultGas()
-	}
-
-	if args.GasPrice.Cmp(big.NewInt(0)) == 0 {
-		args.GasPrice = p.xeth().DefaultGasPrice()
-	}
-
 	*reply, err = p.xeth().Transact(args.From, args.To, args.Value.String(), args.Gas.String(), args.GasPrice.String(), args.Data)
 	if err != nil {
 		return err
diff --git a/xeth/xeth.go b/xeth/xeth.go
index 3d44e292c..e1e25ba09 100644
--- a/xeth/xeth.go
+++ b/xeth/xeth.go
@@ -521,8 +521,8 @@ func (self *XEth) Transact(fromStr, toStr, valueStr, gasStr, gasPriceStr, codeSt
 		from             []byte
 		to               []byte
 		value            = common.NewValue(valueStr)
-		gas              = common.NewValue(gasStr)
-		price            = common.NewValue(gasPriceStr)
+		gas              = common.Big(gasStr)
+		price            = common.Big(gasPriceStr)
 		data             []byte
 		contractCreation bool
 	)
@@ -549,6 +549,16 @@ func (self *XEth) Transact(fromStr, toStr, valueStr, gasStr, gasPriceStr, codeSt
 		}
 	*/
 
+	// TODO: align default values to have the same type, e.g. not depend on
+	// common.Value conversions later on
+	if gas.Cmp(big.NewInt(0)) == 0 {
+		gas = defaultGas
+	}
+
+	if price.Cmp(big.NewInt(0)) == 0 {
+		price = defaultGasPrice
+	}
+
 	from = common.FromHex(fromStr)
 	data = common.FromHex(codeStr)
 	to = common.FromHex(toStr)
@@ -558,9 +568,9 @@ func (self *XEth) Transact(fromStr, toStr, valueStr, gasStr, gasPriceStr, codeSt
 
 	var tx *types.Transaction
 	if contractCreation {
-		tx = types.NewContractCreationTx(value.BigInt(), gas.BigInt(), price.BigInt(), data)
+		tx = types.NewContractCreationTx(value.BigInt(), gas, price, data)
 	} else {
-		tx = types.NewTransactionMessage(to, value.BigInt(), gas.BigInt(), price.BigInt(), data)
+		tx = types.NewTransactionMessage(to, value.BigInt(), gas, price, data)
 	}
 
 	state := self.chainManager.TxState()