diff --git a/build/service-worker-prod.js b/build/service-worker-prod.js
index 1179ec20..8b8493e6 100644
--- a/build/service-worker-prod.js
+++ b/build/service-worker-prod.js
@@ -4,7 +4,7 @@
   // Check to make sure service workers are supported in the current browser,
   // and that the current page is accessed from a secure origin. Using a
   // service worker from an insecure origin will trigger JS console errors.
-  const isLocalhost = Boolean(window.location.hostname === 'localhost' ||
+  var isLocalhost = Boolean(window.location.hostname === 'localhost' ||
       // [::1] is the IPv6 localhost address.
       window.location.hostname === '[::1]' ||
       // 127.0.0.1/8 is considered localhost for IPv4.
@@ -26,7 +26,7 @@
             // i.e. whether there's an existing service worker.
             if (navigator.serviceWorker.controller) {
               // The updatefound event implies that registration.installing is set
-              const installingWorker = registration.installing;
+              var installingWorker = registration.installing;
 
               installingWorker.onstatechange = function() {
                 switch (installingWorker.state) {
diff --git a/build/webpack.prod.conf.js b/build/webpack.prod.conf.js
index 7b4b21c4..9751b880 100644
--- a/build/webpack.prod.conf.js
+++ b/build/webpack.prod.conf.js
@@ -84,8 +84,16 @@ var webpackConfig = merge(baseWebpackConfig, {
       },
       // necessary to consistently work with multiple chunks via CommonsChunkPlugin
       chunksSortMode: 'dependency',
-      serviceWorkerLoader: `<script>${fs.readFileSync(path.join(__dirname,
-        './service-worker-prod.js'), 'utf-8')}</script>`
+      serviceWorkerLoader: (() => {
+        let sw = fs.readFileSync(path.join(__dirname, './service-worker-prod.js'), 'utf-8')
+
+        let result = UglifyJS.minify(sw)
+        if (result.error == null) {
+          sw = result.code
+        }
+
+        return '<script>' + sw + '</script>'
+      })()
     }),
     // split vendor js into its own file
     new webpack.optimize.CommonsChunkPlugin({