Index: .travis.yml
===================================================================
--- .travis.yml	(revision 37031)
+++ .travis.yml	(working copy)
@@ -27,6 +27,8 @@
   - php: hhvm
   - php: nightly
 before_install:
+- nvm install 4
+- node --version
 - WP_CORE_DIR=/tmp/wordpress/
 - git clone https://github.com/WordPress/twentysixteen.git src/wp-content/themes/twentysixteen
 - |
Index: package.json
===================================================================
--- package.json	(revision 37031)
+++ package.json	(working copy)
@@ -8,6 +8,9 @@
   },
   "author": "The WordPress Contributors",
   "license": "GPL-2.0+",
+  "engines": {
+    "node": ">=4.2.1"
+  },
   "devDependencies": {
     "autoprefixer": "~6.3.3",
     "git-or-svn": "~0.1.0",