diff --git a/index.js b/index.js
index 1600cab..e457624 100644
--- a/index.js
+++ b/index.js
@@ -1,6 +1,7 @@
 var assert = require('assert')
 var crypto = require('crypto')
 var pbkdf2 = require('pbkdf2-compat').pbkdf2Sync
+var randomBytes = require('randombytes')
 var unorm = require('unorm')
 
 var DEFAULT_WORDLIST = require('./wordlists/en.json')
@@ -69,7 +70,7 @@ function entropyToMnemonic(entropy, wordlist) {
 
 function generateMnemonic(strength, rng, wordlist) {
   strength = strength || 128
-  rng = rng || crypto.randomBytes
+  rng = rng || randomBytes
 
   var hex = rng(strength / 8).toString('hex')
   return entropyToMnemonic(hex, wordlist)
diff --git a/package.json b/package.json
index 7b373eb..679cd16 100644
--- a/package.json
+++ b/package.json
@@ -22,6 +22,7 @@
   "license": "ISC",
   "dependencies": {
     "pbkdf2-compat": "^2.0.1",
+    "randombytes": "^2.0.1",
     "unorm": "^1.3.3"
   },
   "devDependencies": {
diff --git a/test/index.js b/test/index.js
index 033f2a5..9cbff2c 100644
--- a/test/index.js
+++ b/test/index.js
@@ -1,7 +1,5 @@
 var assert = require('assert')
-var crypto = require('crypto')
 var BIP39 = require('../index.js')
-var sinon = require('sinon')
 
 var wordlists = {
   english: require('../wordlists/en.json'),
@@ -51,13 +49,11 @@ describe('BIP39', function() {
 
   describe('generateMnemonic', function() {
     vectors.english.forEach(function(v, i) {
-      it('works for tests vector ' + i, sinon.test(function() {
-        this.mock(crypto).expects('randomBytes')
-          .exactly(1)
-          .onCall(0).returns(new Buffer(v[0], 'hex'))
+      it('works for tests vector ' + i, function() {
+        function rng() { return new Buffer(v[0], 'hex') }
 
-        assert.equal(BIP39.generateMnemonic(), v[1])
-      }))
+        assert.equal(BIP39.generateMnemonic(undefined, rng), v[1])
+      })
     })
 
     it('can vary generated entropy bit length', function() {