diff --git a/README.md b/README.md
index 622444a..59a5a08 100644
--- a/README.md
+++ b/README.md
@@ -10,6 +10,9 @@ Status:
 
 This micro-lib allows you to provide a script which sets an environment using unix style and have it work on windows too
 
+## Prerequisites
+-   [Node.js](https://nodejs.org/) version 4.0 or greater.
+
 ## Usage
 
 I use this in my npm scripts:
diff --git a/package.json b/package.json
index bcc2136..e4c1bbc 100644
--- a/package.json
+++ b/package.json
@@ -6,6 +6,9 @@
   "bin": {
     "cross-env": "bin/cross-env.js"
   },
+  "engines": {
+    "node" : ">=4.0"
+  },
   "scripts": {
     "start": "npm run test:watch",
     "prebuild": "rimraf dist && mkdir dist",