diff --git a/core/types/transaction.go b/core/types/transaction.go
index 9c6e77be98..7b53cac2c6 100644
--- a/core/types/transaction.go
+++ b/core/types/transaction.go
@@ -153,16 +153,21 @@ func (tx *Transaction) UnmarshalJSON(input []byte) error {
 	if err := dec.UnmarshalJSON(input); err != nil {
 		return err
 	}
-	var V byte
-	if isProtectedV(dec.V) {
-		chainID := deriveChainId(dec.V).Uint64()
-		V = byte(dec.V.Uint64() - 35 - 2*chainID)
-	} else {
-		V = byte(dec.V.Uint64() - 27)
-	}
-	if !crypto.ValidateSignatureValues(V, dec.R, dec.S, false) {
-		return ErrInvalidSig
+
+	withSignature := dec.V.Sign() != 0 || dec.R.Sign() != 0 || dec.S.Sign() != 0
+	if withSignature {
+		var V byte
+		if isProtectedV(dec.V) {
+			chainID := deriveChainId(dec.V).Uint64()
+			V = byte(dec.V.Uint64() - 35 - 2*chainID)
+		} else {
+			V = byte(dec.V.Uint64() - 27)
+		}
+		if !crypto.ValidateSignatureValues(V, dec.R, dec.S, false) {
+			return ErrInvalidSig
+		}
 	}
+
 	*tx = Transaction{data: dec}
 	return nil
 }
diff --git a/core/types/transaction_test.go b/core/types/transaction_test.go
index b390f45c67..f38d8e7177 100644
--- a/core/types/transaction_test.go
+++ b/core/types/transaction_test.go
@@ -185,6 +185,7 @@ func TestTransactionJSON(t *testing.T) {
 	}
 	signer := NewEIP155Signer(common.Big1)
 
+	transactions := make([]*Transaction, 0, 50)
 	for i := uint64(0); i < 25; i++ {
 		var tx *Transaction
 		switch i % 2 {
@@ -193,20 +194,25 @@ func TestTransactionJSON(t *testing.T) {
 		case 1:
 			tx = NewContractCreation(i, common.Big0, 1, common.Big2, []byte("abcdef"))
 		}
+		transactions = append(transactions, tx)
 
-		tx, err := SignTx(tx, signer, key)
+		signedTx, err := SignTx(tx, signer, key)
 		if err != nil {
 			t.Fatalf("could not sign transaction: %v", err)
 		}
 
+		transactions = append(transactions, signedTx)
+	}
+
+	for _, tx := range transactions {
 		data, err := json.Marshal(tx)
 		if err != nil {
-			t.Errorf("json.Marshal failed: %v", err)
+			t.Fatalf("json.Marshal failed: %v", err)
 		}
 
 		var parsedTx *Transaction
 		if err := json.Unmarshal(data, &parsedTx); err != nil {
-			t.Errorf("json.Unmarshal failed: %v", err)
+			t.Fatalf("json.Unmarshal failed: %v", err)
 		}
 
 		// compare nonce, price, gaslimit, recipient, amount, payload, V, R, S