diff --git a/tools/build_config.js b/tools/build_config.js
index ad103a20d7..9cb9cd2697 100644
--- a/tools/build_config.js
+++ b/tools/build_config.js
@@ -60,6 +60,8 @@ module.exports = {
       ascii_only: true
     },
     compress: {
+      ecma: 2015,
+      unsafe_arrows: true,
       passes: 2,
       unsafe: true,
       warnings: true,