diff --git a/nightwatch.js b/nightwatch.js
index 3a817bf5de..2b02d9e989 100644
--- a/nightwatch.js
+++ b/nightwatch.js
@@ -62,8 +62,8 @@ module.exports = {
       'desiredCapabilities': {
         'browserName': 'safari',
         'javascriptEnabled': true,
-        'platform': 'OS X 10.11',
-        'version': '9.0',
+        'platform': 'OS X 10.10',
+        'version': '8.0',
         'acceptSslCerts': true,
         'build': 'build-' + TRAVIS_JOB_NUMBER,
         'tunnel-identifier': 'remix_tests_' + TRAVIS_JOB_NUMBER
diff --git a/package.json b/package.json
index f4318b021d..6be9f42e93 100644
--- a/package.json
+++ b/package.json
@@ -17,6 +17,9 @@
     "which": "^1.2.10"
   },
   "devDependencies": {
+    "babel-cli": "^6.16.0",
+    "babel-plugin-transform-es2015-block-scoping": "^6.15.0",
+    "babel-plugin-transform-es2015-template-literals": "^6.8.0",
     "browserify": "^13.0.1",
     "ethereumjs-util": "^4.5.0",
     "http-server": "^0.9.0",
@@ -32,7 +35,7 @@
     "start_node": "./runNode.sh",
     "start_eth": "eth -j --rpccorsdomain '*'",
     "start_geth": "geth --rpc --rpcapi 'web3,eth,debug' --rpcport 8545 --rpccorsdomain '*'",
-    "build": "mkdir build; browserify src/index.js -g yo-yoify -o build/app.js",
+    "build": "mkdir build; browserify src/index.js -g yo-yoify -o build/app.js; babel --plugins babel-plugin-transform-es2015-template-literals,babel-plugin-transform-es2015-block-scoping build/app.js --out-file build/app.js",
     "test": "standard && tape ./test/tests.js",
     "serve": "http-server .",
     "nightwatch_local": "nightwatch --config nightwatch.js --env local",
diff --git a/src/helpers/util.js b/src/helpers/util.js
index fafa61faa5..756ac4fe5b 100644
--- a/src/helpers/util.js
+++ b/src/helpers/util.js
@@ -7,7 +7,11 @@ module.exports = {
     var ret = '0x'
     for (var i = 0; i < ints.length; i++) {
       var h = ints[i]
-      ret += (h <= 0xf ? '0' : '') + h.toString(16)
+      if (h) {
+        ret += (h <= 0xf ? '0' : '') + h.toString(16)
+      } else {
+        ret += '00'
+      }
     }
     return ret
   },