diff --git a/lib/bip32.js b/lib/bip32.js
index 4e84fff86..ffac16be9 100644
--- a/lib/bip32.js
+++ b/lib/bip32.js
@@ -8,15 +8,9 @@ var Random = require('./random');
 var bn = require('./bn');
 var constants = require('./constants');
 
-var BIP32 = function BIP32(str) {
+var BIP32 = function BIP32() {
   if (!(this instanceof BIP32))
-    return new BIP32(str);
-  if (str === 'testnet' || str === 'mainnet') {
-    this.version = constants[str].bip32privkey;
-    this.fromRandom();
-  }
-  else if (str)
-    this.fromString(str);
+    return new BIP32();
 }
 
 BIP32.prototype.fromRandom = function(network) {
@@ -48,6 +42,8 @@ BIP32.prototype.fromString = function(str) {
 
   if (bytes !== undefined && bytes !== null)
     this.initFromBytes(bytes);
+
+  return this;
 };
 
 BIP32.prototype.fromSeed = function(bytes, network) {
diff --git a/test/test.bip32.js b/test/test.bip32.js
index 971318f1d..82643b7e7 100644
--- a/test/test.bip32.js
+++ b/test/test.bip32.js
@@ -43,224 +43,224 @@ describe('BIP32', function() {
   });
 
   it('should initialize test vector 1 from the extended public key', function() {
-    var bip32 = new BIP32(vector1_m_public);
+    var bip32 = new BIP32().fromString(vector1_m_public);
     should.exist(bip32);
   });
 
   it('should initialize test vector 1 from the extended private key', function() {
-    var bip32 = new BIP32(vector1_m_private);
+    var bip32 = new BIP32().fromString(vector1_m_private);
     should.exist(bip32);
   });
 
   it('should get the extended public key from the extended private key for test vector 1', function() {
-    var bip32 = new BIP32(vector1_m_private);
+    var bip32 = new BIP32().fromString(vector1_m_private);
     bip32.extendedPublicKeyString().should.equal(vector1_m_public);
   });
 
   it("should get m/0' ext. private key from test vector 1", function() {
-    var bip32 = new BIP32(vector1_m_private);
+    var bip32 = new BIP32().fromString(vector1_m_private);
     var child = bip32.derive("m/0'");
     should.exist(child);
     child.extendedPrivateKeyString().should.equal(vector1_m0h_private);
   });
 
   it("should get m/0' ext. public key from test vector 1", function() {
-    var bip32 = new BIP32(vector1_m_private);
+    var bip32 = new BIP32().fromString(vector1_m_private);
     var child = bip32.derive("m/0'");
     should.exist(child);
     child.extendedPublicKeyString().should.equal(vector1_m0h_public);
   });
 
   it("should get m/0'/1 ext. private key from test vector 1", function() {
-    var bip32 = new BIP32(vector1_m_private);
+    var bip32 = new BIP32().fromString(vector1_m_private);
     var child = bip32.derive("m/0'/1");
     should.exist(child);
     child.extendedPrivateKeyString().should.equal(vector1_m0h1_private);
   });
 
   it("should get m/0'/1 ext. public key from test vector 1", function() {
-    var bip32 = new BIP32(vector1_m_private);
+    var bip32 = new BIP32().fromString(vector1_m_private);
     var child = bip32.derive("m/0'/1");
     should.exist(child);
     child.extendedPublicKeyString().should.equal(vector1_m0h1_public);
   });
 
   it("should get m/0'/1 ext. public key from m/0' public key from test vector 1", function() {
-    var bip32 = new BIP32(vector1_m_private);
+    var bip32 = new BIP32().fromString(vector1_m_private);
     var child = bip32.derive("m/0'");
-    var child_pub = new BIP32(child.extendedPublicKeyString());
+    var child_pub = new BIP32().fromString(child.extendedPublicKeyString());
     var child2 = child_pub.derive("m/1");
     should.exist(child2);
     child2.extendedPublicKeyString().should.equal(vector1_m0h1_public);
   });
 
   it("should get m/0'/1/2h ext. private key from test vector 1", function() {
-    var bip32 = new BIP32(vector1_m_private);
+    var bip32 = new BIP32().fromString(vector1_m_private);
     var child = bip32.derive("m/0'/1/2'");
     should.exist(child);
     child.extendedPrivateKeyString().should.equal(vector1_m0h12h_private);
   });
 
   it("should get m/0'/1/2h ext. public key from test vector 1", function() {
-    var bip32 = new BIP32(vector1_m_private);
+    var bip32 = new BIP32().fromString(vector1_m_private);
     var child = bip32.derive("m/0'/1/2'");
     should.exist(child);
     child.extendedPublicKeyString().should.equal(vector1_m0h12h_public);
   });
 
   it("should get m/0'/1/2h/2 ext. private key from test vector 1", function() {
-    var bip32 = new BIP32(vector1_m_private);
+    var bip32 = new BIP32().fromString(vector1_m_private);
     var child = bip32.derive("m/0'/1/2'/2");
     should.exist(child);
     child.extendedPrivateKeyString().should.equal(vector1_m0h12h2_private);
   });
 
   it("should get m/0'/1/2'/2 ext. public key from m/0'/1/2' public key from test vector 1", function() {
-    var bip32 = new BIP32(vector1_m_private);
+    var bip32 = new BIP32().fromString(vector1_m_private);
     var child = bip32.derive("m/0'/1/2'");
-    var child_pub = new BIP32(child.extendedPublicKeyString());
+    var child_pub = new BIP32().fromString(child.extendedPublicKeyString());
     var child2 = child_pub.derive("m/2");
     should.exist(child2);
     child2.extendedPublicKeyString().should.equal(vector1_m0h12h2_public);
   });
 
   it("should get m/0'/1/2h/2 ext. public key from test vector 1", function() {
-    var bip32 = new BIP32(vector1_m_private);
+    var bip32 = new BIP32().fromString(vector1_m_private);
     var child = bip32.derive("m/0'/1/2'/2");
     should.exist(child);
     child.extendedPublicKeyString().should.equal(vector1_m0h12h2_public);
   });
 
   it("should get m/0'/1/2h/2/1000000000 ext. private key from test vector 1", function() {
-    var bip32 = new BIP32(vector1_m_private);
+    var bip32 = new BIP32().fromString(vector1_m_private);
     var child = bip32.derive("m/0'/1/2'/2/1000000000");
     should.exist(child);
     child.extendedPrivateKeyString().should.equal(vector1_m0h12h21000000000_private);
   });
 
   it("should get m/0'/1/2h/2/1000000000 ext. public key from test vector 1", function() {
-    var bip32 = new BIP32(vector1_m_private);
+    var bip32 = new BIP32().fromString(vector1_m_private);
     var child = bip32.derive("m/0'/1/2'/2/1000000000");
     should.exist(child);
     child.extendedPublicKeyString().should.equal(vector1_m0h12h21000000000_public);
   });
 
   it("should get m/0'/1/2'/2/1000000000 ext. public key from m/0'/1/2'/2 public key from test vector 1", function() {
-    var bip32 = new BIP32(vector1_m_private);
+    var bip32 = new BIP32().fromString(vector1_m_private);
     var child = bip32.derive("m/0'/1/2'/2");
-    var child_pub = new BIP32(child.extendedPublicKeyString());
+    var child_pub = new BIP32().fromString(child.extendedPublicKeyString());
     var child2 = child_pub.derive("m/1000000000");
     should.exist(child2);
     child2.extendedPublicKeyString().should.equal(vector1_m0h12h21000000000_public);
   });
 
   it('should initialize test vector 2 from the extended public key', function() {
-    var bip32 = new BIP32(vector2_m_public);
+    var bip32 = new BIP32().fromString(vector2_m_public);
     should.exist(bip32);
   });
 
   it('should initialize test vector 2 from the extended private key', function() {
-    var bip32 = new BIP32(vector2_m_private);
+    var bip32 = new BIP32().fromString(vector2_m_private);
     should.exist(bip32);
   });
 
   it('should get the extended public key from the extended private key for test vector 2', function() {
-    var bip32 = new BIP32(vector2_m_private);
+    var bip32 = new BIP32().fromString(vector2_m_private);
     bip32.extendedPublicKeyString().should.equal(vector2_m_public);
   });
 
   it("should get m/0 ext. private key from test vector 2", function() {
-    var bip32 = new BIP32(vector2_m_private);
+    var bip32 = new BIP32().fromString(vector2_m_private);
     var child = bip32.derive("m/0");
     should.exist(child);
     child.extendedPrivateKeyString().should.equal(vector2_m0_private);
   });
 
   it("should get m/0 ext. public key from test vector 2", function() {
-    var bip32 = new BIP32(vector2_m_private);
+    var bip32 = new BIP32().fromString(vector2_m_private);
     var child = bip32.derive("m/0");
     should.exist(child);
     child.extendedPublicKeyString().should.equal(vector2_m0_public);
   });
 
   it("should get m/0 ext. public key from m public key from test vector 2", function() {
-    var bip32 = new BIP32(vector2_m_private);
+    var bip32 = new BIP32().fromString(vector2_m_private);
     var child = bip32.derive("m");
-    var child_pub = new BIP32(child.extendedPublicKeyString());
+    var child_pub = new BIP32().fromString(child.extendedPublicKeyString());
     var child2 = child_pub.derive("m/0");
     should.exist(child2);
     child2.extendedPublicKeyString().should.equal(vector2_m0_public);
   });
 
   it("should get m/0/2147483647h ext. private key from test vector 2", function() {
-    var bip32 = new BIP32(vector2_m_private);
+    var bip32 = new BIP32().fromString(vector2_m_private);
     var child = bip32.derive("m/0/2147483647'");
     should.exist(child);
     child.extendedPrivateKeyString().should.equal(vector2_m02147483647h_private);
   });
 
   it("should get m/0/2147483647h ext. public key from test vector 2", function() {
-    var bip32 = new BIP32(vector2_m_private);
+    var bip32 = new BIP32().fromString(vector2_m_private);
     var child = bip32.derive("m/0/2147483647'");
     should.exist(child);
     child.extendedPublicKeyString().should.equal(vector2_m02147483647h_public);
   });
 
   it("should get m/0/2147483647h/1 ext. private key from test vector 2", function() {
-    var bip32 = new BIP32(vector2_m_private);
+    var bip32 = new BIP32().fromString(vector2_m_private);
     var child = bip32.derive("m/0/2147483647'/1");
     should.exist(child);
     child.extendedPrivateKeyString().should.equal(vector2_m02147483647h1_private);
   });
 
   it("should get m/0/2147483647h/1 ext. public key from test vector 2", function() {
-    var bip32 = new BIP32(vector2_m_private);
+    var bip32 = new BIP32().fromString(vector2_m_private);
     var child = bip32.derive("m/0/2147483647'/1");
     should.exist(child);
     child.extendedPublicKeyString().should.equal(vector2_m02147483647h1_public);
   });
 
   it("should get m/0/2147483647h/1 ext. public key from m/0/2147483647h public key from test vector 2", function() {
-    var bip32 = new BIP32(vector2_m_private);
+    var bip32 = new BIP32().fromString(vector2_m_private);
     var child = bip32.derive("m/0/2147483647'");
-    var child_pub = new BIP32(child.extendedPublicKeyString());
+    var child_pub = new BIP32().fromString(child.extendedPublicKeyString());
     var child2 = child_pub.derive("m/1");
     should.exist(child2);
     child2.extendedPublicKeyString().should.equal(vector2_m02147483647h1_public);
   });
 
   it("should get m/0/2147483647h/1/2147483646h ext. private key from test vector 2", function() {
-    var bip32 = new BIP32(vector2_m_private);
+    var bip32 = new BIP32().fromString(vector2_m_private);
     var child = bip32.derive("m/0/2147483647'/1/2147483646'");
     should.exist(child);
     child.extendedPrivateKeyString().should.equal(vector2_m02147483647h12147483646h_private);
   });
 
   it("should get m/0/2147483647h/1/2147483646h ext. public key from test vector 2", function() {
-    var bip32 = new BIP32(vector2_m_private);
+    var bip32 = new BIP32().fromString(vector2_m_private);
     var child = bip32.derive("m/0/2147483647'/1/2147483646'");
     should.exist(child);
     child.extendedPublicKeyString().should.equal(vector2_m02147483647h12147483646h_public);
   });
 
   it("should get m/0/2147483647h/1/2147483646h/2 ext. private key from test vector 2", function() {
-    var bip32 = new BIP32(vector2_m_private);
+    var bip32 = new BIP32().fromString(vector2_m_private);
     var child = bip32.derive("m/0/2147483647'/1/2147483646'/2");
     should.exist(child);
     child.extendedPrivateKeyString().should.equal(vector2_m02147483647h12147483646h2_private);
   });
 
   it("should get m/0/2147483647h/1/2147483646h/2 ext. public key from test vector 2", function() {
-    var bip32 = new BIP32(vector2_m_private);
+    var bip32 = new BIP32().fromString(vector2_m_private);
     var child = bip32.derive("m/0/2147483647'/1/2147483646'/2");
     should.exist(child);
     child.extendedPublicKeyString().should.equal(vector2_m02147483647h12147483646h2_public);
   });
 
   it("should get m/0/2147483647h/1/2147483646h/2 ext. public key from m/0/2147483647h/2147483646h public key from test vector 2", function() {
-    var bip32 = new BIP32(vector2_m_private);
+    var bip32 = new BIP32().fromString(vector2_m_private);
     var child = bip32.derive("m/0/2147483647'/1/2147483646'");
-    var child_pub = new BIP32(child.extendedPublicKeyString());
+    var child_pub = new BIP32().fromString(child.extendedPublicKeyString());
     var child2 = child_pub.derive("m/2");
     should.exist(child2);
     child2.extendedPublicKeyString().should.equal(vector2_m02147483647h12147483646h2_public);
@@ -289,7 +289,7 @@ describe('BIP32', function() {
     it('should initialize a new BIP32 correctly from a random BIP32', function() {
       var b1 = new BIP32();
       b1.fromRandom('testnet');
-      var b2 = new BIP32(b1.extendedPublicKeyString());
+      var b2 = new BIP32().fromString(b1.extendedPublicKeyString());
       b2.extendedPublicKeyString().should.equal(b1.extendedPublicKeyString());
     });
 
@@ -311,7 +311,7 @@ describe('BIP32', function() {
     });
 
     it('should return an xpub string', function() {
-      var bip32b = new BIP32(bip32.extendedPublicKeyString());
+      var bip32b = new BIP32().fromString(bip32.extendedPublicKeyString());
       bip32b.toString().slice(0, 4).should.equal('xpub');
     });
 
@@ -320,7 +320,7 @@ describe('BIP32', function() {
     });
 
     it('should return a tpub string', function() {
-      var tip32b = new BIP32(tip32.extendedPublicKeyString());
+      var tip32b = new BIP32().fromString(tip32.extendedPublicKeyString());
       tip32b.toString().slice(0, 4).should.equal('tpub');
     });