--- /dev/null
+++ b/.babelrc
@@ -0,0 +1,7 @@
+{
+  "presets": [
+    ["es2015", {
+      "loose": false,
+    }],
+  ],
+}
--- a/package.json
+++ b/package.json
@@ -16,7 +16,7 @@
     "name": "Mike Bostock",
     "url": "http://bost.ocks.org/mike"
   },
-  "main": "build/d3-shape.js",
+  "main": "lib/index.js",
   "module": "index",
   "jsnext:main": "index",
   "repository": {