diff --git a/lib/address.js b/lib/address.js
index 31c68fa..6b17756 100644
--- a/lib/address.js
+++ b/lib/address.js
@@ -22,7 +22,7 @@ var Hash = require('./crypto/hash');
  *
  * // get an address from a public key
  * var address = Address(publicKey, 'testnet').toString();
- * 
+ *
  *
  * @param {String} data - The encoded data in various formats
  * @param {String} [network] - The network: 'livenet' or 'testnet'
@@ -71,10 +71,20 @@ function Address(data, network, type) {
   info.network = info.network || network || networks.defaultNetwork.name;
   info.type = info.type || type || 'pubkeyhash';
 
-  // set the validated values
-  this.hashBuffer = info.hashBuffer;
-  this.network = info.network;
-  this.type = info.type;
+  Object.defineProperty(this, 'hashBuffer', {
+    configurable: false,
+    value: info.hashBuffer
+  });
+
+  Object.defineProperty(this, 'network', {
+    configurable: false,
+    value: info.network
+  });
+
+  Object.defineProperty(this, 'type', {
+    configurable: false,
+    value: info.type
+  });
 
   return this;
 
@@ -132,7 +142,7 @@ Address._transformBuffer = function(buffer, network, type){
       bufNetwork = 'livenet';
       bufType = 'scripthash';
       break;
-    
+
     case networks.testnet.pubkeyhash:
       bufNetwork = 'testnet';
       bufType = 'pubkeyhash';
@@ -143,7 +153,7 @@ Address._transformBuffer = function(buffer, network, type){
       bufType = 'scripthash';
       break;
   }
-  
+
   if (!bufNetwork || (network && network !== bufNetwork)) {
     throw new TypeError('Address has mismatched network type.');
   }
diff --git a/lib/privatekey.js b/lib/privatekey.js
index 5754ffb..d5333d7 100644
--- a/lib/privatekey.js
+++ b/lib/privatekey.js
@@ -67,9 +67,20 @@ var PrivateKey = function PrivateKey(data, network, compressed) {
     throw new TypeError('Must specify whether the corresponding public key is compressed or not (true or false)');
   }
 
-  this.bn = info.bn;
-  this.compressed = info.compressed;
-  this.network = info.network;
+  Object.defineProperty(this, 'bn', {
+    configurable: false,
+    value: info.bn
+  });
+
+  Object.defineProperty(this, 'compressed', {
+    configurable: false,
+    value: info.compressed
+  });
+
+  Object.defineProperty(this, 'network', {
+    configurable: false,
+    value: info.network
+  });
 
   return this;
 
diff --git a/lib/publickey.js b/lib/publickey.js
index 2c25d12..b777a89 100644
--- a/lib/publickey.js
+++ b/lib/publickey.js
@@ -12,10 +12,10 @@ var Address = require('./address');
  *
  * // instantiate from a private key
  * var key = PublicKey(privateKey, true);
- * 
- * // export to as a DER hex encoded string 
+ *
+ * // export to as a DER hex encoded string
  * var exported = key.toString();
- * 
+ *
  * // import the public key
  * var imported = PublicKey.fromString(exported);
  *
@@ -45,7 +45,7 @@ var PublicKey = function PublicKey(data, compressed) {
     info = PublicKey._transformDER(new Buffer(data, 'hex' ));
   } else if (data instanceof Buffer || data instanceof Uint8Array){
     info = PublicKey._transformDER(data);
-  } else if (data.constructor && (data.constructor.name && 
+  } else if (data.constructor && (data.constructor.name &&
                                   data.constructor.name === 'PrivateKey')) {
     info = PublicKey._transformPrivateKey(data);
   } else {
@@ -55,8 +55,15 @@ var PublicKey = function PublicKey(data, compressed) {
   // validation
   info.point.validate();
 
-  this.point = info.point;
-  this.compressed = info.compressed;
+  Object.defineProperty(this, 'point', {
+    configurable: false,
+    value: info.point
+  });
+
+  Object.defineProperty(this, 'compressed', {
+    configurable: false,
+    value: info.compressed
+  });
 
   return this;
 
@@ -71,7 +78,7 @@ var PublicKey = function PublicKey(data, compressed) {
  */
 PublicKey._transformPrivateKey = function(privkey) {
   var info = {};
-  if (!privkey.constructor || 
+  if (!privkey.constructor ||
       (privkey.constructor.name && privkey.constructor.name !== 'PrivateKey')) {
     throw new TypeError('Must be an instance of PrivateKey');
   }
diff --git a/test/privatekey.js b/test/privatekey.js
index 1a69f48..f523345 100644
--- a/test/privatekey.js
+++ b/test/privatekey.js
@@ -263,16 +263,14 @@ describe('PrivateKey', function() {
 
     it('should convert this known PrivateKey to known PublicKey and preserve compressed=true', function() {
       var privhex = '906977a061af29276e40bf377042ffbde414e496ae2260bbf1fa9d085637bfff';
-      var privkey = new PrivateKey(BN(new Buffer(privhex, 'hex')));
-      privkey.compressed = true;
+      var privkey = new PrivateKey(BN(new Buffer(privhex, 'hex')), 'livenet', true);
       var pubkey = privkey.toPublicKey();
       pubkey.compressed.should.equal(true);
     });
 
     it('should convert this known PrivateKey to known PublicKey and preserve compressed=true', function() {
       var privhex = '906977a061af29276e40bf377042ffbde414e496ae2260bbf1fa9d085637bfff';
-      var privkey = new PrivateKey(BN(new Buffer(privhex, 'hex')));
-      privkey.compressed = false;
+      var privkey = new PrivateKey(BN(new Buffer(privhex, 'hex')), 'livenet', false);
       var pubkey = privkey.toPublicKey();
       pubkey.compressed.should.equal(false);
     });