diff --git a/lib/bitcoind.js b/lib/bitcoind.js
index ca13ceef..399f52b3 100644
--- a/lib/bitcoind.js
+++ b/lib/bitcoind.js
@@ -307,6 +307,8 @@ Bitcoin.prototype.close = function(callback) {
  * Block
  */
 
+var _blockFlag = {};
+
 function Block(data) {
   if (!(this instanceof Block)) {
     return new Block(data);
@@ -318,7 +320,7 @@ function Block(data) {
 
   var self = this;
 
-  this._isBlock = Block._blockFlag;
+  this._blockFlag = _blockFlag;
 
   Object.keys(data).forEach(function(key) {
     if (!self[key]) {
@@ -331,10 +333,8 @@ function Block(data) {
   this.toHex();
 }
 
-Block._blockFlag = {};
-
 Block.isBlock = function(block) {
-  return block._isBlock === Block._blockFlag;
+  return block._blockFlag === _blockFlag;
 };
 
 // NOTE: Could just call tx.GetHash() in C++
@@ -442,6 +442,8 @@ Block.toHex = function(block) {
  * Transaction
  */
 
+var _txFlag = {};
+
 function Transaction(data) {
   if (!(this instanceof Transaction)) {
     return new Transaction(data);
@@ -453,7 +455,7 @@ function Transaction(data) {
 
   var self = this;
 
-  this._isTx = Transaction._txFlag;
+  this._txFlag = _txFlag;
 
   this.nMinTxFee = data.nMinTxFee || data.minTxFee || 1000;
   this.nMinRelayTxFee = data.nMinRelayTxFee || data.minRelayTxFee || 1000;
@@ -481,11 +483,9 @@ function Transaction(data) {
   this.toHex();
 }
 
-Transaction._txFlag = {};
-
 Transaction.isTransaction =
 Transaction.isTx = function(tx) {
-  return tx._isTx === Transaction._txFlag;
+  return tx._txFlag === _txFlag;
 };
 
 Transaction.prototype.verify = function() {