diff --git a/common/bytes.go b/common/bytes.go
index 2d885ac74..5bdacd810 100644
--- a/common/bytes.go
+++ b/common/bytes.go
@@ -127,6 +127,11 @@ func CopyBytes(b []byte) (copiedBytes []byte) {
 	return
 }
 
+func HasHexPrefix(str string) bool {
+	l := len(str)
+	return l >= 2 && str[0:2] == "0x"
+}
+
 func IsHex(str string) bool {
 	l := len(str)
 	return l >= 4 && l%2 == 0 && str[0:2] == "0x"
diff --git a/rpc/args.go b/rpc/args.go
index a8cb7dcb1..cebabf4ba 100644
--- a/rpc/args.go
+++ b/rpc/args.go
@@ -41,7 +41,11 @@ func blockHeight(raw interface{}, number *int64) error {
 	case "pending":
 		*number = -2
 	default:
-		*number = common.String2Big(str).Int64()
+		if common.HasHexPrefix(str) {
+			*number = common.String2Big(str).Int64()
+		} else {
+			return NewInvalidTypeError("blockNumber", "is not a valid string")
+		}
 	}
 
 	return nil