diff --git a/src/hdwallet.js b/src/hdwallet.js
index acc7764..98cf7b8 100644
--- a/src/hdwallet.js
+++ b/src/hdwallet.js
@@ -15,6 +15,10 @@ var HDWallet = module.exports = function(seed, network) {
     var I = Crypto.HMAC(Crypto.SHA512, seed, 'Bitcoin seed', { asBytes: true })
     this.chaincode = I.slice(32)
     this.network = network || 'mainnet'
+    if(!Network.hasOwnProperty(this.network)) {
+      throw new Error("Unknown network: " + this.network)
+    }
+
     this.priv = new ECKey(I.slice(0, 32).concat([1]), true, this.getKeyVersion())
     this.pub = this.priv.getPub()
     this.index = 0
diff --git a/test/hdwallet.js b/test/hdwallet.js
index 974c06e..85d2ae4 100644
--- a/test/hdwallet.js
+++ b/test/hdwallet.js
@@ -1,7 +1,10 @@
 /* global describe, it */
 var HDWallet = require('../src/hdwallet.js')
-, assert = require('assert')
-, convert = require('../src/convert.js')
+var assert = require('assert')
+var convert = require('../src/convert.js')
+var Network = require('../src/network')
+var mainnet = Network.mainnet.addressVersion
+var testnet = Network.testnet.addressVersion
 
 var b2h = convert.bytesToHex
 
@@ -214,4 +217,32 @@ describe('HDWallet', function() {
             assert.equal(hd.toBase58(true), 'xprvA2nrNbFZABcdryreWet9Ea4LvTJcGsqrMzxHx98MMrotbir7yrKCEXw7nadnHM8Dq38EGfSh6dqA9QWTyefMLEcBYJUuekgW4BYPJcr9E7j')
         })
     })
+
+    describe('network types', function() {
+        it('ensures that a mainnet Wallet has mainnet child keys (pub and priv)', function() {
+            var wallet = new HDWallet("foobar", "mainnet")
+            assert.equal(wallet.priv.version, mainnet)
+
+            var privChild = wallet.derivePrivate(0)
+            assert.equal(privChild.priv.version, mainnet)
+
+            var pubChild = wallet.derive(0)
+            assert.equal(pubChild.priv.version, mainnet)
+        })
+
+        it('ensures that a testnet Wallet has testnet child keys (pub and priv)', function() {
+            var wallet = new HDWallet("foobar", "testnet")
+            assert.equal(wallet.priv.version, testnet)
+
+            var privChild = wallet.derivePrivate(0)
+            assert.equal(privChild.priv.version, testnet)
+
+            var pubChild = wallet.derive(0)
+            assert.equal(pubChild.priv.version, testnet)
+        })
+
+        it('throws an excption when unknown network type is passed in', function() {
+            assert.throws(function() { new HDWallet("foobar", "doge") })
+        })
+    })
 })
diff --git a/test/wallet.js b/test/wallet.js
index 44474ac..650ad5c 100644
--- a/test/wallet.js
+++ b/test/wallet.js
@@ -1,7 +1,4 @@
 var Wallet = require('../src/wallet.js')
-var Network = require('../src/network')
-var mainnet = Network.mainnet.addressVersion
-var testnet = Network.testnet.addressVersion
 var assert = require('assert')
 
 describe('Wallet', function() {
@@ -37,19 +34,4 @@ describe('Wallet', function() {
     })
   })
 
-  describe('networkType', function() {
-    it('ensures that a mainnet Wallet has mainnet child keys (pub and priv)', function() {
-        var w = Wallet("foobar", {network: "mainnet"})
-        assert(w.getMasterKey().priv.version == mainnet)
-        w.generateAddress()
-        assert(w.getPrivateKey(0).priv.version == mainnet)
-    })
-
-    it('ensures that a testnet Wallet has testnet child keys (pub and priv)', function() {
-        var w = Wallet("foobar", {network: "testnet"})
-        assert(w.getMasterKey().priv.version == testnet)
-        w.generateAddress()
-        assert(w.getPrivateKey(0).priv.version == testnet)
-    })
-  })
 })