diff --git a/.travis.yml b/.travis.yml
index c7e5d33..78fe6b2 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,3 +3,4 @@ cache: yarn
 node_js:
   - '7'
   - '6'
+  - '4'
diff --git a/cli.js b/cli.js
index 79b0083..3309aab 100755
--- a/cli.js
+++ b/cli.js
@@ -1,16 +1,18 @@
 #!/usr/bin/env node
 
-const { spawn } = require('child_process')
-const { bin, cwd, args, isYarn, isNPM } = require('./index')
+'use strict'
 
-if (!isYarn && !isNPM) {
+const spawn = require('child_process').spawn
+const nyr = require('./index')
+
+if (!nyr.isYarn && !nyr.isNPM) {
   throw new Error('Expected to be launched from either npm or yarn.')
 }
 
-if (args.length < 2) {
+if (nyr.args.length < 2) {
   throw new Error('Expected at least one argument with what script to run.')
 }
 
-const child = spawn(bin, args, { cwd, stdio: 'inherit' })
+const child = spawn(nyr.bin, nyr.args, { cwd: nyr.cwd, stdio: 'inherit' })
 
 child.on('exit', code => process.exit(code))
diff --git a/index.js b/index.js
index c9c18fb..21c81ea 100755
--- a/index.js
+++ b/index.js
@@ -1,10 +1,7 @@
-const {
-  env: { npm_execpath: bin, DEBUG },
-  argv,
-  cwd,
-} = process
+'use strict'
 
-const args = argv.slice(2)
+const bin = process.env.npm_execpath
+const args = process.argv.slice(2)
 
 if (args[0] !== 'run') {
   args.unshift('run')
@@ -13,13 +10,13 @@ if (args[0] !== 'run') {
 module.exports = {
   bin,
   args,
-  cwd: cwd(),
+  cwd: process.cwd(),
   isYarn: bin.endsWith('yarn.js'),
   isNPM: bin.endsWith('npm-cli.js'),
 }
 
-if (DEBUG === 'nyr') {
-  const { inspect } = require('util')
+if (process.env.DEBUG === 'nyr') {
+  const inspect = require('util').inspect
   const colors = process.stdout.isTTY
   console.log(
     '-- nyr DEBUG START --\n%s\n-- nyr DEBUG END --',
diff --git a/package.json b/package.json
index 2436311..7ab72a3 100644
--- a/package.json
+++ b/package.json
@@ -22,7 +22,7 @@
     "start": "DEBUG=nyr node ./index.js"
   },
   "engine": {
-    "node": ">=6"
+    "node": ">=4"
   },
   "devDependencies": {
     "@simonkberg/eslint-config": "^5.0.0",
diff --git a/test/index.js b/test/index.js
index c9f13b8..c5571dd 100644
--- a/test/index.js
+++ b/test/index.js
@@ -1,5 +1,4 @@
-const { spawn } = require('child_process')
-const { assign } = Object
+const spawn = require('child_process').spawn
 const options = {
   cwd: process.cwd(),
   stdio: 'inherit',
@@ -7,12 +6,7 @@ const options = {
 
 const run = name => new Promise((resolve, reject) => {
   const args = ['run', `test:${name}`]
-  const opts = assign({}, options, {
-    env: assign({}, process.env, {
-      _: name,
-    }),
-  })
-  const child = spawn(name, args, opts)
+  const child = spawn(name, args, options)
 
   child.on('error', err => reject(err))
   child.on('exit', code =>
diff --git a/test/npm.js b/test/npm.js
index ba65486..a8a7f2b 100644
--- a/test/npm.js
+++ b/test/npm.js
@@ -1,8 +1,8 @@
 const assert = require('assert')
-const { bin, args, cwd, isYarn, isNPM } = require('../index')
+const nyr = require('../index')
 
-assert(bin.endsWith('npm-cli.js'), `'bin' is '${bin}'`)
-assert(args.indexOf('run') === 0, `'args' is '${args}'`)
-assert(cwd === process.cwd(), `'cwd' is '${cwd}'`)
-assert(isYarn === false, `'isYarn' is '${isYarn}'`)
-assert(isNPM === true, `'isNPM' is '${isNPM}'`)
+assert(nyr.bin.endsWith('npm-cli.js'), `'bin' is '${nyr.bin}'`)
+assert(nyr.args.indexOf('run') === 0, `'args' is '${nyr.args}'`)
+assert(nyr.cwd === process.cwd(), `'cwd' is '${nyr.cwd}'`)
+assert(nyr.isYarn === false, `'isYarn' is '${nyr.isYarn}'`)
+assert(nyr.isNPM === true, `'isNPM' is '${nyr.isNPM}'`)
diff --git a/test/yarn.js b/test/yarn.js
index 9e4b827..10be038 100644
--- a/test/yarn.js
+++ b/test/yarn.js
@@ -1,8 +1,8 @@
 const assert = require('assert')
-const { bin, args, cwd, isYarn, isNPM } = require('../index')
+const nyr = require('../index')
 
-assert(bin.endsWith('yarn.js'), `'bin' is '${bin}'`)
-assert(args.indexOf('run') === 0, `'args' is '${args}'`)
-assert(cwd === process.cwd(), `'cwd' is '${cwd}'`)
-assert(isYarn === true, `'isYarn' is '${isYarn}'`)
-assert(isNPM === false, `'isNPM' is '${isNPM}'`)
+assert(nyr.bin.endsWith('yarn.js'), `'bin' is '${nyr.bin}'`)
+assert(nyr.args.indexOf('run') === 0, `'args' is '${nyr.args}'`)
+assert(nyr.cwd === process.cwd(), `'cwd' is '${nyr.cwd}'`)
+assert(nyr.isYarn === true, `'isYarn' is '${nyr.isYarn}'`)
+assert(nyr.isNPM === false, `'isNPM' is '${nyr.isNPM}'`)