diff --git a/.eslintrc b/.eslintrc
index f34b41d..6edac35 100644
--- a/.eslintrc
+++ b/.eslintrc
@@ -1,7 +1,7 @@
 {
     "root": true,
     "extends": [
-        "@satazor/eslint-config/es5",
+        "@satazor/eslint-config/es6",
         "@satazor/eslint-config/addons/node"
     ]
-}
\ No newline at end of file
+}
diff --git a/.travis.yml b/.travis.yml
index 57a922d..8c7c0f3 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,7 +1,6 @@
 language: node_js
 node_js:
-  - '0.10'
-  - '0.12'
   - '4'
   - '6'
-  - '7'
+  - 'node'
+  - 'lts/*'
diff --git a/CHANGELOG.md b/CHANGELOG.md
index f1298a8..093109b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,20 @@
+## 6.0.0 - 2017-11-11
+
+- Remove NodeJS v0.10 and v0.12 support
+- Change escaping on Windows to use `^` instead of quotes:
+    - Fix a bug that made it impossible to escape an argument that contained quotes followed by `>` or other special chars, e.g.: `"foo|bar"`, fixes [#82](https://github.com/IndigoUnited/node-cross-spawn/issues/82)
+    - Fix a bug were a command containing `%x%` would be replaced with the contents of the `x` environment variable, fixes [#51](https://github.com/IndigoUnited/node-cross-spawn/issues/51)
+- Fix `options` argument being mutated
+
+
+## 5.1.1 - 2017-02-26
+
+- Fix `options.shell` support for NodeJS [v4.8](https://github.com/nodejs/node/blob/master/doc/changelogs/CHANGELOG_V4.md#4.8.0)
+
+## 5.0.1 - 2016-11-04
+
+- Fix `options.shell` support for NodeJS v7
+
 ## 5.0.0 - 2016-10-30
 
 - Add support for `options.shell`
diff --git a/README.md b/README.md
index 0664183..eca6083 100644
--- a/README.md
+++ b/README.md
@@ -23,10 +23,6 @@ A cross platform solution to node's spawn and spawnSync.
 
 `$ npm install cross-spawn`
 
-If you are using `spawnSync` on node 0.10 or older, you will also need to install `spawn-sync`:
-
-`$ npm install spawn-sync`
-
 
 ## Why
 
@@ -35,7 +31,7 @@ Node has issues when using spawn on Windows:
 - It ignores [PATHEXT](https://github.com/joyent/node/issues/2318)
 - It does not support [shebangs](http://pt.wikipedia.org/wiki/Shebang)
 - No `options.shell` support on node `<v4.8`
-- It does not allow you to run `del` or `dir`
+- Has problems running commands with [spaces](https://github.com/nodejs/node/issues/7367)
 
 All these issues are handled correctly by `cross-spawn`.
 There are some known modules, such as [win-spawn](https://github.com/ForbesLindesay/win-spawn), that try to solve this but they are either broken or provide faulty escaping of shell arguments.
@@ -59,18 +55,23 @@ var results = spawn.sync('npm', ['list', '-g', '-depth', '0'], { stdio: 'inherit
 
 ## Caveats
 
-#### `options.shell` as an alternative to `cross-spawn`
+### Using `options.shell` as an alternative to `cross-spawn`
 
 Starting from node `v4.8`, `spawn` has a `shell` option that allows you run commands from within a shell. This new option solves most of the problems that `cross-spawn` attempts to solve, but:
 
 - It's not supported in node `<v4.8`
-- It has no support for shebangs on Windows
 - You must manually escape the command and arguments which is very error prone, specially when passing user input
 
 If you are using the `shell` option to spawn a command in a cross platform way, consider using `cross-spawn` instead. You have been warned.
 
+### `options.shell` support
+
+While `cross-spawn` adds support for `options.shell` in node `<v4.8`, all of its enhancements are disabled.
+
+This mimics the Node.js behavior. More specifically, the command and its arguments will not be automatically escaped nor shebang support will be offered. This is by design because if you are using `options.shell` you are probably targeting a specific platform anyway and you don't want things to get into your way.
+
 
-#### Shebangs
+### Shebangs support
 
 While `cross-spawn` handles shebangs on Windows, its support is limited: e.g.: it doesn't handle arguments after the path, e.g.: `#!/bin/bash -e`.
 
diff --git a/appveyor.yml b/appveyor.yml
index 5874e49..e1cd59d 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -11,11 +11,10 @@ init:
 # what combinations to test
 environment:
   matrix:
-    - nodejs_version: 0.10
-    - nodejs_version: 0.12
     - nodejs_version: 4
     - nodejs_version: 6
-    - nodejs_version: 7
+    - nodejs_version: 8
+    - nodejs_version: 9
 
 # get the latest stable version of Node 0.STABLE.latest
 install:
diff --git a/index.js b/index.js
index 7814a96..5509742 100644
--- a/index.js
+++ b/index.js
@@ -1,20 +1,15 @@
 'use strict';
 
-var cp = require('child_process');
-var parse = require('./lib/parse');
-var enoent = require('./lib/enoent');
-
-var cpSpawnSync = cp.spawnSync;
+const cp = require('child_process');
+const parse = require('./lib/parse');
+const enoent = require('./lib/enoent');
 
 function spawn(command, args, options) {
-    var parsed;
-    var spawned;
-
     // Parse the arguments
-    parsed = parse(command, args, options);
+    const parsed = parse(command, args, options);
 
     // Spawn the child process
-    spawned = cp.spawn(parsed.command, parsed.args, parsed.options);
+    const spawned = cp.spawn(parsed.command, parsed.args, parsed.options);
 
     // Hook into child process "exit" event to emit an error if the command
     // does not exists, see: https://github.com/IndigoUnited/node-cross-spawn/issues/16
@@ -24,28 +19,13 @@ function spawn(command, args, options) {
 }
 
 function spawnSync(command, args, options) {
-    var parsed;
-    var result;
-
-    if (!cpSpawnSync) {
-        try {
-            cpSpawnSync = require('spawn-sync');  // eslint-disable-line global-require
-        } catch (ex) {
-            throw new Error(
-                'In order to use spawnSync on node 0.10 or older, you must ' +
-                'install spawn-sync:\n\n' +
-                '  npm install spawn-sync --save'
-            );
-        }
-    }
-
     // Parse the arguments
-    parsed = parse(command, args, options);
+    const parsed = parse(command, args, options);
 
     // Spawn the child process
-    result = cpSpawnSync(parsed.command, parsed.args, parsed.options);
+    const result = cp.spawnSync(parsed.command, parsed.args, parsed.options);
 
-    // Analyze if the command does not exists, see: https://github.com/IndigoUnited/node-cross-spawn/issues/16
+    // Analyze if the command does not exist, see: https://github.com/IndigoUnited/node-cross-spawn/issues/16
     result.error = result.error || enoent.verifyENOENTSync(result.status, parsed);
 
     return result;
diff --git a/lib/enoent.js b/lib/enoent.js
index d0a193a..514740a 100644
--- a/lib/enoent.js
+++ b/lib/enoent.js
@@ -1,43 +1,35 @@
 'use strict';
 
-var isWin = process.platform === 'win32';
-var resolveCommand = require('./util/resolveCommand');
-
-var isNode10 = process.version.indexOf('v0.10.') === 0;
+const isWin = process.platform === 'win32';
 
 function notFoundError(command, syscall) {
-    var err;
-
-    err = new Error(syscall + ' ' + command + ' ENOENT');
-    err.code = err.errno = 'ENOENT';
-    err.syscall = syscall + ' ' + command;
-
-    return err;
+    return Object.assign(new Error(`${syscall} ${command} ENOENT`), {
+        code: 'ENOENT',
+        errno: 'ENOENT',
+        syscall: `${syscall} ${command}`,
+    });
 }
 
 function hookChildProcess(cp, parsed) {
-    var originalEmit;
-
     if (!isWin) {
         return;
     }
 
-    originalEmit = cp.emit;
-    cp.emit = function (name, arg1) {
-        var err;
+    const originalEmit = cp.emit;
 
+    cp.emit = function (name, arg1) {
         // If emitting "exit" event and exit code is 1, we need to check if
         // the command exists and emit an "error" instead
         // See: https://github.com/IndigoUnited/node-cross-spawn/issues/16
         if (name === 'exit') {
-            err = verifyENOENT(arg1, parsed, 'spawn');
+            const err = verifyENOENT(arg1, parsed, 'spawn');
 
             if (err) {
                 return originalEmit.call(cp, 'error', err);
             }
         }
 
-        return originalEmit.apply(cp, arguments);
+        return originalEmit.apply(cp, arguments);  // eslint-disable-line prefer-rest-params
     };
 }
 
@@ -54,16 +46,6 @@ function verifyENOENTSync(status, parsed) {
         return notFoundError(parsed.original, 'spawnSync');
     }
 
-    // If we are in node 10, then we are using spawn-sync; if it exited
-    // with -1 it probably means that the command does not exist
-    if (isNode10 && status === -1) {
-        parsed.file = isWin ? parsed.file : resolveCommand(parsed.original);
-
-        if (!parsed.file) {
-            return notFoundError(parsed.original, 'spawnSync');
-        }
-    }
-
     return null;
 }
 
diff --git a/lib/parse.js b/lib/parse.js
index 10a0136..b3974f8 100644
--- a/lib/parse.js
+++ b/lib/parse.js
@@ -1,51 +1,52 @@
 'use strict';
 
-var resolveCommand = require('./util/resolveCommand');
-var hasEmptyArgumentBug = require('./util/hasEmptyArgumentBug');
-var escapeArgument = require('./util/escapeArgument');
-var escapeCommand = require('./util/escapeCommand');
-var readShebang = require('./util/readShebang');
+const resolveCommand = require('./util/resolveCommand');
+const escapeArgument = require('./util/escapeArgument');
+const readShebang = require('./util/readShebang');
 
-var isWin = process.platform === 'win32';
-var skipShellRegExp = /\.(?:com|exe)$/i;
+const isWin = process.platform === 'win32';
+const isExecutableRegExp = /\.(?:com|exe)$/i;
 
 // Supported in Node >= 6 and >= 4.8
-var supportsShellOption = parseInt(process.version.substr(1).split('.')[0], 10) >= 6 ||
- parseInt(process.version.substr(1).split('.')[0], 10) === 4 && parseInt(process.version.substr(1).split('.')[1], 10) >= 8;
+const supportsShellOption =
+    parseInt(process.version.substr(1).split('.')[0], 10) >= 6 ||
+    (parseInt(process.version.substr(1).split('.')[0], 10) === 4 && parseInt(process.version.substr(1).split('.')[1], 10) >= 8);
 
-function parseNonShell(parsed) {
-    var shebang;
-    var needsShell;
-    var applyQuotes;
+function detectShebang(parsed) {
+    parsed.file = resolveCommand(parsed.command) || resolveCommand(parsed.command, true);
+
+    const shebang = parsed.file && readShebang(parsed.file);
+
+    if (shebang) {
+        parsed.args.unshift(parsed.file);
+        parsed.command = shebang;
+
+        return resolveCommand(shebang) || resolveCommand(shebang, true);
+    }
+
+    return parsed.file;
+}
 
+function parseNonShell(parsed) {
     if (!isWin) {
         return parsed;
     }
 
     // Detect & add support for shebangs
-    parsed.file = resolveCommand(parsed.command);
-    parsed.file = parsed.file || resolveCommand(parsed.command, true);
-    shebang = parsed.file && readShebang(parsed.file);
+    const commandFile = detectShebang(parsed);
 
-    if (shebang) {
-        parsed.args.unshift(parsed.file);
-        parsed.command = shebang;
-        needsShell = hasEmptyArgumentBug || !skipShellRegExp.test(resolveCommand(shebang) || resolveCommand(shebang, true));
-    } else {
-        needsShell = hasEmptyArgumentBug || !skipShellRegExp.test(parsed.file);
-    }
+    // We don't need a shell if the command filename is an executable
+    const needsShell = !isExecutableRegExp.test(commandFile);
 
     // If a shell is required, use cmd.exe and take care of escaping everything correctly
     if (needsShell) {
         // Escape command & arguments
-        applyQuotes = (parsed.command !== 'echo');  // Do not quote arguments for the special "echo" command
-        parsed.command = escapeCommand(parsed.command);
-        parsed.args = parsed.args.map(function (arg) {
-            return escapeArgument(arg, applyQuotes);
-        });
-
-        // Make use of cmd.exe
-        parsed.args = ['/d', '/s', '/c', '"' + parsed.command + (parsed.args.length ? ' ' + parsed.args.join(' ') : '') + '"'];
+        parsed.command = escapeArgument(parsed.command);
+        parsed.args = parsed.args.map(escapeArgument);
+
+        const shellCommand = [parsed.command].concat(parsed.args).join(' ');
+
+        parsed.args = ['/d', '/s', '/c', `"${shellCommand}"`];
         parsed.command = process.env.comspec || 'cmd.exe';
         parsed.options.windowsVerbatimArguments = true;  // Tell node's spawn that the arguments are already escaped
     }
@@ -54,19 +55,17 @@ function parseNonShell(parsed) {
 }
 
 function parseShell(parsed) {
-    var shellCommand;
-
     // If node supports the shell option, there's no need to mimic its behavior
     if (supportsShellOption) {
         return parsed;
     }
 
     // Mimic node shell option, see: https://github.com/nodejs/node/blob/b9f6a2dc059a1062776133f3d4fd848c4da7d150/lib/child_process.js#L335
-    shellCommand = [parsed.command].concat(parsed.args).join(' ');
+    const shellCommand = [parsed.command].concat(parsed.args).join(' ');
 
     if (isWin) {
         parsed.command = typeof parsed.options.shell === 'string' ? parsed.options.shell : process.env.comspec || 'cmd.exe';
-        parsed.args = ['/d', '/s', '/c', '"' + shellCommand + '"'];
+        parsed.args = ['/d', '/s', '/c', `"${shellCommand}"`];
         parsed.options.windowsVerbatimArguments = true;  // Tell node's spawn that the arguments are already escaped
     } else {
         if (typeof parsed.options.shell === 'string') {
@@ -86,8 +85,6 @@ function parseShell(parsed) {
 // ------------------------------------------------
 
 function parse(command, args, options) {
-    var parsed;
-
     // Normalize arguments, similar to nodejs
     if (args && !Array.isArray(args)) {
         options = args;
@@ -95,13 +92,13 @@ function parse(command, args, options) {
     }
 
     args = args ? args.slice(0) : [];  // Clone array to avoid changing the original
-    options = options || {};
+    options = Object.assign({}, options);  // Clone object to avoid changing the original
 
     // Build our parsed object
-    parsed = {
-        command: command,
-        args: args,
-        options: options,
+    const parsed = {
+        command,
+        args,
+        options,
         file: undefined,
         original: command,
     };
diff --git a/lib/util/escapeArgument.js b/lib/util/escapeArgument.js
index 367263f..1021102 100644
--- a/lib/util/escapeArgument.js
+++ b/lib/util/escapeArgument.js
@@ -1,30 +1,26 @@
 'use strict';
 
-function escapeArgument(arg, quote) {
+const isWin = process.platform === 'win32';
+
+function escapeArgumentWindows(arg) {
     // Convert to string
-    arg = '' + arg;
-
-    // If we are not going to quote the argument,
-    // escape shell metacharacters, including double and single quotes:
-    if (!quote) {
-        arg = arg.replace(/([()%!^<>&|;,"'\s])/g, '^$1');
-    } else {
-        // Sequence of backslashes followed by a double quote:
-        // double up all the backslashes and escape the double quote
-        arg = arg.replace(/(\\*)"/g, '$1$1\\"');
-
-        // Sequence of backslashes followed by the end of the string
-        // (which will become a double quote later):
-        // double up all the backslashes
-        arg = arg.replace(/(\\*)$/, '$1$1');
-
-        // All other backslashes occur literally
-
-        // Quote the whole thing:
-        arg = '"' + arg + '"';
-    }
+    arg = `${arg}`;
+
+    // Escape quotes with \^
+    arg = arg.replace(/"/g, '\\^$1');
+
+    // Escape other meta chars with ^
+    arg = arg.replace(/([()%!^<>&|;,\s])/g, '^$1');
 
     return arg;
 }
 
-module.exports = escapeArgument;
+function escapeArgumentUnix(arg) {
+    if (/^[a-z0-9_-]+$/i.test(arg)) {
+        return arg;
+    }
+
+    return `"${arg.replace('\'', "'\\'")}"`;
+}
+
+module.exports = isWin ? escapeArgumentWindows : escapeArgumentUnix;
diff --git a/lib/util/escapeCommand.js b/lib/util/escapeCommand.js
deleted file mode 100644
index d9c25b2..0000000
--- a/lib/util/escapeCommand.js
+++ /dev/null
@@ -1,12 +0,0 @@
-'use strict';
-
-var escapeArgument = require('./escapeArgument');
-
-function escapeCommand(command) {
-    // Do not escape if this command is not dangerous..
-    // We do this so that commands like "echo" or "ifconfig" work
-    // Quoting them, will make them unaccessible
-    return /^[a-z0-9_-]+$/i.test(command) ? command : escapeArgument(command, true);
-}
-
-module.exports = escapeCommand;
diff --git a/lib/util/hasEmptyArgumentBug.js b/lib/util/hasEmptyArgumentBug.js
deleted file mode 100644
index 9f2eba6..0000000
--- a/lib/util/hasEmptyArgumentBug.js
+++ /dev/null
@@ -1,18 +0,0 @@
-'use strict';
-
-// See: https://github.com/IndigoUnited/node-cross-spawn/pull/34#issuecomment-221623455
-function hasEmptyArgumentBug() {
-    var nodeVer;
-
-    if (process.platform !== 'win32') {
-        return false;
-    }
-
-    nodeVer = process.version.substr(1).split('.').map(function (num) {
-        return parseInt(num, 10);
-    });
-
-    return (nodeVer[0] === 0 && nodeVer[1] < 12);
-}
-
-module.exports = hasEmptyArgumentBug();
diff --git a/lib/util/readShebang.js b/lib/util/readShebang.js
index 2cf3541..031fefc 100644
--- a/lib/util/readShebang.js
+++ b/lib/util/readShebang.js
@@ -1,23 +1,22 @@
 'use strict';
 
-var fs = require('fs');
-var LRU = require('lru-cache');
-var shebangCommand = require('shebang-command');
+const fs = require('fs');
+const LRU = require('lru-cache');
+const shebangCommand = require('shebang-command');
 
-var shebangCache = new LRU({ max: 50, maxAge: 30 * 1000 });  // Cache just for 30sec
+const shebangCache = new LRU({ max: 50, maxAge: 30 * 1000 });  // Cache just for 30sec
 
 function readShebang(command) {
-    var buffer;
-    var fd;
-    var shebang;
+    let shebang = shebangCache.get(command);
 
     // Check if it is in the cache first
-    if (shebangCache.has(command)) {
-        return shebangCache.get(command);
+    if (shebang) {
+        return shebang;
     }
 
     // Read the first 150 bytes from the file
-    buffer = new Buffer(150);
+    let fd;
+    const buffer = new Buffer(150);
 
     try {
         fd = fs.openSync(command, 'r');
diff --git a/lib/util/resolveCommand.js b/lib/util/resolveCommand.js
index b7a9490..0ff0893 100644
--- a/lib/util/resolveCommand.js
+++ b/lib/util/resolveCommand.js
@@ -1,20 +1,20 @@
 'use strict';
 
-var path = require('path');
-var which = require('which');
-var LRU = require('lru-cache');
+const path = require('path');
+const which = require('which');
+const LRU = require('lru-cache');
 
-var commandCache = new LRU({ max: 50, maxAge: 30 * 1000 });  // Cache just for 30sec
+const commandCache = new LRU({ max: 50, maxAge: 30 * 1000 });  // Cache just for 30sec
 
 function resolveCommand(command, noExtension) {
-    var resolved;
-
     noExtension = !!noExtension;
-    resolved = commandCache.get(command + '!' + noExtension);
+
+    const cacheId = `${command}!${noExtension}`;
+    let resolved = commandCache.get(cacheId);
 
     // Check if its resolved in the cache
-    if (commandCache.has(command)) {
-        return commandCache.get(command);
+    if (resolved) {
+        return resolved;
     }
 
     try {
@@ -23,7 +23,7 @@ function resolveCommand(command, noExtension) {
             which.sync(command, { pathExt: path.delimiter + (process.env.PATHEXT || '') });
     } catch (e) { /* empty */ }
 
-    commandCache.set(command + '!' + noExtension, resolved);
+    commandCache.set(cacheId, resolved);
 
     return resolved;
 }
diff --git a/package.json b/package.json
index 7c10c97..bf29379 100644
--- a/package.json
+++ b/package.json
@@ -46,8 +46,11 @@
     "expect.js": "^0.3.0",
     "glob": "^7.0.0",
     "mkdirp": "^0.5.1",
-    "mocha": "^3.0.2",
+    "mocha": "^4.0.0",
     "once": "^1.4.0",
     "rimraf": "^2.5.0"
+  },
+  "engines": {
+    "node": ">=4.8"
   }
 }
diff --git a/test/.eslintrc b/test/.eslintrc
index 32a5d9a..92c6c5b 100644
--- a/test/.eslintrc
+++ b/test/.eslintrc
@@ -5,6 +5,7 @@
     "rules": {
         "no-invalid-this": 0,
         "max-nested-callbacks": 0,
-        "callback-return": 0
+        "callback-return": 0,
+        "prefer-template": 0,
     }
-}
\ No newline at end of file
+}
diff --git a/test/fixtures/%CD% b/test/fixtures/%CD%
new file mode 100755
index 0000000..051009c
--- /dev/null
+++ b/test/fixtures/%CD%
@@ -0,0 +1,3 @@
+#!/bin/bash
+
+echo special
diff --git a/test/fixtures/%CD%.bat b/test/fixtures/%CD%.bat
new file mode 100755
index 0000000..f248e1f
--- /dev/null
+++ b/test/fixtures/%CD%.bat
@@ -0,0 +1,2 @@
+@echo off
+echo special
diff --git a/test/fixtures/echo.js b/test/fixtures/echo.js
index 133540b..b14f68d 100755
--- a/test/fixtures/echo.js
+++ b/test/fixtures/echo.js
@@ -1,7 +1,7 @@
 'use strict';
 
-var args = process.argv.slice(2);
+const args = process.argv.slice(2);
 
-args.forEach(function (arg, index) {
+args.forEach((arg, index) => {
     process.stdout.write(arg + (index < args.length - 1 ? '\n' : ''));
 });
diff --git a/test/fixtures/win-ppid.js b/test/fixtures/win-ppid.js
index e9d03ff..8702fbc 100644
--- a/test/fixtures/win-ppid.js
+++ b/test/fixtures/win-ppid.js
@@ -1,11 +1,14 @@
 #!/usr/bin/env node
 
-var spawnSync = require('child_process').spawnSync || require('spawn-sync');
+'use strict';
+
+const spawnSync = require('child_process').spawnSync;
 
 function ppidSync() {
-    var res = spawnSync('wmic',
-        ['process', 'where', '(processid=' + process.pid + ')', 'get', 'parentprocessid']);
-    var lines = res.stdout.toString().split(/\r?\n/);
+    const res = spawnSync('wmic',
+        ['process', 'where', `(processid=${process.pid})`, 'get', 'parentprocessid']);
+    const lines = res.stdout.toString().split(/\r?\n/);
+
     return parseInt(lines[1].trim(), 10);
 }
 
diff --git a/test/prepare.js b/test/prepare.js
index ba83714..9a223b0 100644
--- a/test/prepare.js
+++ b/test/prepare.js
@@ -1,17 +1,17 @@
 'use strict';
 
-var glob = require('glob');
-var fs = require('fs');
-var path = require('path');
-var buffered = require('./util/buffered');
+const glob = require('glob');
+const fs = require('fs');
+const path = require('path');
+const buffered = require('./util/buffered');
 
 
 // Preare fixtures
-var fixturesDir = __dirname + '/fixtures';
+const fixturesDir = __dirname + '/fixtures';
 
-glob.sync('prepare_*', { cwd: __dirname + '/fixtures' }).forEach(function (file) {
-    var contents = fs.readFileSync(fixturesDir + '/' + file);
-    var finalFile = file.replace(/^prepare_/, '').replace(/\.sh$/, '');
+glob.sync('prepare_*', { cwd: __dirname + '/fixtures' }).forEach((file) => {
+    const contents = fs.readFileSync(fixturesDir + '/' + file);
+    const finalFile = file.replace(/^prepare_/, '').replace(/\.sh$/, '');
 
     fs.writeFileSync(fixturesDir + '/' + finalFile, contents);
     fs.chmodSync(fixturesDir + '/' + finalFile, parseInt('0777', 8));
@@ -22,7 +22,7 @@ glob.sync('prepare_*', { cwd: __dirname + '/fixtures' }).forEach(function (file)
 // Install spawn-sync for older node versions
 if (/^v0\.10\./.test(process.version)) {
     process.stdout.write('Installing spawn-sync..\n');
-    buffered('spawn', 'npm', ['install', 'spawn-sync'], { stdio: 'inherit' }, function (err) {
+    buffered('spawn', 'npm', ['install', 'spawn-sync'], { stdio: 'inherit' }, (err) => {
         if (err) {
             throw err;
         }
@@ -35,8 +35,6 @@ if (/^v0\.10\./.test(process.version)) {
 if (process.env.APPVEYOR) {
     process.env.PATH = process.env.PATH
     .split(path.delimiter)
-    .filter(function (entry) {
-        return !/\\git\\bin$/i.test(path.normalize(entry));
-    })
+    .filter((entry) => !/\\git\\bin$/i.test(path.normalize(entry)))
     .join(path.delimiter);
 }
diff --git a/test/test.js b/test/test.js
index 7e506ee..3fa3b18 100644
--- a/test/test.js
+++ b/test/test.js
@@ -1,24 +1,23 @@
 'use strict';
 
-var fs = require('fs');
-var path = require('path');
-var expect = require('expect.js');
-var rimraf = require('rimraf');
-var mkdirp = require('mkdirp');
-var hasEmptyArgumentBug = require('../lib/util/hasEmptyArgumentBug');
-var spawn = require('../');
-var buffered = require('./util/buffered');
+const fs = require('fs');
+const path = require('path');
+const expect = require('expect.js');
+const rimraf = require('rimraf');
+const mkdirp = require('mkdirp');
+const spawn = require('../');
+const buffered = require('./util/buffered');
 
-var isWin = process.platform === 'win32';
+const isWin = process.platform === 'win32';
 
-describe('cross-spawn', function () {
-    var methods = ['spawn', 'sync'];
+describe('cross-spawn', () => {
+    const methods = ['spawn', 'sync'];
 
-    methods.forEach(function (method) {
-        describe(method, function () {
-            var originalPath = process.env.PATH;
+    methods.forEach((method) => {
+        describe(method, () => {
+            const originalPath = process.env.PATH;
 
-            before(function () {
+            before(() => {
                 mkdirp.sync(__dirname + '/tmp');
             });
 
@@ -26,18 +25,18 @@ describe('cross-spawn', function () {
                 // Give it some time, RIMRAF was giving problems on windows
                 this.timeout(10000);
 
-                rimraf(__dirname + '/tmp', function () {
+                rimraf(__dirname + '/tmp', () => {
                     // Ignore errors, RIMRAF was giving problems on windows
                     next(null);
                 });
             });
 
-            afterEach(function () {
+            afterEach(() => {
                 process.env.PATH = originalPath;
             });
 
-            it('should support shebang in executables with /usr/bin/env', function (next) {
-                buffered(method, __dirname + '/fixtures/shebang', function (err, data, code) {
+            it('should support shebang in executables with /usr/bin/env', (next) => {
+                buffered(method, __dirname + '/fixtures/shebang', (err, data, code) => {
                     expect(err).to.not.be.ok();
                     expect(code).to.be(0);
                     expect(data).to.equal('shebang works!');
@@ -45,7 +44,7 @@ describe('cross-spawn', function () {
                     // Test if the actual shebang file is resolved against the PATH
                     process.env.PATH = path.normalize(__dirname + '/fixtures/') + path.delimiter + process.env.PATH;
 
-                    buffered(method, 'shebang', function (err, data, code) {
+                    buffered(method, 'shebang', (err, data, code) => {
                         expect(err).to.not.be.ok();
                         expect(code).to.be(0);
                         expect(data).to.equal('shebang works!');
@@ -55,14 +54,14 @@ describe('cross-spawn', function () {
                 });
             });
 
-            it('should support shebang in executables with relative path', function (next) {
-                var executable = './' + path.relative(process.cwd(), __dirname + '/fixtures/shebang');
+            it('should support shebang in executables with relative path', (next) => {
+                const executable = './' + path.relative(process.cwd(), __dirname + '/fixtures/shebang');
 
                 fs.writeFileSync(__dirname + '/tmp/shebang', '#!/usr/bin/env node\n\nprocess.stdout.write(\'yeah\');',
                     { mode: parseInt('0777', 8) });
                 process.env.PATH = path.normalize(__dirname + '/tmp/') + path.delimiter + process.env.PATH;
 
-                buffered(method, executable, function (err, data, code) {
+                buffered(method, executable, (err, data, code) => {
                     expect(err).to.not.be.ok();
                     expect(code).to.be(0);
                     expect(data).to.equal('shebang works!');
@@ -71,14 +70,15 @@ describe('cross-spawn', function () {
                 });
             });
 
-            it('should support shebang in executables with relative path that starts with `..`', function (next) {
-                var executable = '../' + path.basename(process.cwd()) + '/' + path.relative(process.cwd(), __dirname + '/fixtures/shebang');
+            it('should support shebang in executables with relative path that starts with `..`', (next) => {
+                const executable = '../' + path.basename(process.cwd()) +
+                    '/' + path.relative(process.cwd(), __dirname + '/fixtures/shebang');
 
                 fs.writeFileSync(__dirname + '/tmp/shebang', '#!/usr/bin/env node\n\nprocess.stdout.write(\'yeah\');',
                     { mode: parseInt('0777', 8) });
                 process.env.PATH = path.normalize(__dirname + '/tmp/') + path.delimiter + process.env.PATH;
 
-                buffered(method, executable, function (err, data, code) {
+                buffered(method, executable, (err, data, code) => {
                     expect(err).to.not.be.ok();
                     expect(code).to.be(0);
                     expect(data).to.equal('shebang works!');
@@ -87,12 +87,12 @@ describe('cross-spawn', function () {
                 });
             });
 
-            it('should support shebang in executables with extensions', function (next) {
+            it('should support shebang in executables with extensions', (next) => {
                 fs.writeFileSync(__dirname + '/tmp/shebang_' + method + '.js', '#!/usr/bin/env node\n\nprocess.stdout.write(\'shebang with \
 extension\');', { mode: parseInt('0777', 8) });
                 process.env.PATH = path.normalize(__dirname + '/tmp/') + path.delimiter + process.env.PATH;
 
-                buffered(method, __dirname + '/tmp/shebang_' + method + '.js', function (err, data, code) {
+                buffered(method, __dirname + '/tmp/shebang_' + method + '.js', (err, data, code) => {
                     expect(err).to.not.be.ok();
                     expect(code).to.be(0);
                     expect(data).to.equal('shebang with extension');
@@ -100,7 +100,7 @@ extension\');', { mode: parseInt('0777', 8) });
                     // Test if the actual shebang file is resolved against the PATH
                     process.env.PATH = path.normalize(__dirname + '/fixtures/') + path.delimiter + process.env.PATH;
 
-                    buffered(method, 'shebang_' + method + '.js', function (err, data, code) {
+                    buffered(method, 'shebang_' + method + '.js', (err, data, code) => {
                         expect(err).to.not.be.ok();
                         expect(code).to.be(0);
                         expect(data).to.equal('shebang with extension');
@@ -110,8 +110,8 @@ extension\');', { mode: parseInt('0777', 8) });
                 });
             });
 
-            it('should expand using PATHEXT properly', function (next) {
-                buffered(method, __dirname + '/fixtures/foo', function (err, data, code) {
+            it('should expand using PATHEXT properly', (next) => {
+                buffered(method, __dirname + '/fixtures/foo', (err, data, code) => {
                     expect(err).to.not.be.ok();
                     expect(code).to.be(0);
                     expect(data.trim()).to.equal('foo');
@@ -120,8 +120,8 @@ extension\');', { mode: parseInt('0777', 8) });
                 });
             });
 
-            it('should handle commands with spaces', function (next) {
-                buffered(method, __dirname + '/fixtures/bar space', function (err, data, code) {
+            it('should handle commands with spaces', (next) => {
+                buffered(method, __dirname + '/fixtures/bar space', (err, data, code) => {
                     expect(err).to.not.be.ok();
                     expect(code).to.be(0);
                     expect(data.trim()).to.equal('bar');
@@ -130,8 +130,8 @@ extension\');', { mode: parseInt('0777', 8) });
                 });
             });
 
-            it('should handle commands with special shell chars', function (next) {
-                buffered(method, __dirname + '/fixtures/()%!^&;, ', function (err, data, code) {
+            it('should handle commands with special shell chars', (next) => {
+                buffered(method, __dirname + '/fixtures/()%!^&;, ', (err, data, code) => {
                     expect(err).to.not.be.ok();
                     expect(code).to.be(0);
                     expect(data.trim()).to.equal('special');
@@ -140,12 +140,12 @@ extension\');', { mode: parseInt('0777', 8) });
                 });
             });
 
-            it('should handle arguments with quotes', function (next) {
+            it('should handle arguments with quotes', (next) => {
                 buffered(method, 'node', [
                     __dirname + '/fixtures/echo',
                     '"foo"',
                     'foo"bar"foo',
-                ], function (err, data, code) {
+                ], (err, data, code) => {
                     expect(err).to.not.be.ok();
                     expect(code).to.be(0);
                     expect(data).to.equal('"foo"\nfoo"bar"foo');
@@ -154,13 +154,13 @@ extension\');', { mode: parseInt('0777', 8) });
                 });
             });
 
-            it('should handle empty arguments', function (next) {
+            it('should handle empty arguments', (next) => {
                 buffered(method, 'node', [
                     __dirname + '/fixtures/echo',
                     'foo',
                     '',
                     'bar',
-                ], function (err, data, code) {
+                ], (err, data, code) => {
                     expect(err).to.not.be.ok();
                     expect(code).to.be(0);
                     expect(data).to.equal('foo\n\nbar');
@@ -169,7 +169,7 @@ extension\');', { mode: parseInt('0777', 8) });
                         'foo',
                         '',
                         'bar',
-                    ], function (err, data, code) {
+                    ], (err, data, code) => {
                         expect(err).to.not.be.ok();
                         expect(code).to.be(0);
                         expect(data.trim()).to.equal('foo  bar');
@@ -179,11 +179,11 @@ extension\');', { mode: parseInt('0777', 8) });
                 });
             });
 
-            it('should handle non-string arguments', function (next) {
+            it('should handle non-string arguments', (next) => {
                 buffered(method, 'node', [
                     __dirname + '/fixtures/echo',
                     1234,
-                ], function (err, data, code) {
+                ], (err, data, code) => {
                     expect(err).to.not.be.ok();
                     expect(code).to.be(0);
                     expect(data).to.equal('1234');
@@ -192,12 +192,12 @@ extension\');', { mode: parseInt('0777', 8) });
                 });
             });
 
-            it('should handle arguments with spaces', function (next) {
+            it('should handle arguments with spaces', (next) => {
                 buffered(method, 'node', [
                     __dirname + '/fixtures/echo',
                     'I am',
                     'André Cruz',
-                ], function (err, data, code) {
+                ], (err, data, code) => {
                     expect(err).to.not.be.ok();
                     expect(code).to.be(0);
                     expect(data).to.equal('I am\nAndré Cruz');
@@ -206,13 +206,13 @@ extension\');', { mode: parseInt('0777', 8) });
                 });
             });
 
-            it('should handle arguments with \\"', function (next) {
+            it('should handle arguments with \\"', (next) => {
                 buffered(method, 'node', [
                     __dirname + '/fixtures/echo',
                     'foo',
                     '\\"',
                     'bar',
-                ], function (err, data, code) {
+                ], (err, data, code) => {
                     expect(err).to.not.be.ok();
                     expect(code).to.be(0);
                     expect(data).to.equal('foo\n\\"\nbar');
@@ -221,13 +221,13 @@ extension\');', { mode: parseInt('0777', 8) });
                 });
             });
 
-            it('should handle arguments that end with \\', function (next) {
+            it('should handle arguments that end with \\', (next) => {
                 buffered(method, 'node', [
                     __dirname + '/fixtures/echo',
                     'foo',
                     'bar\\',
                     'baz',
-                ], function (err, data, code) {
+                ], (err, data, code) => {
                     expect(err).to.not.be.ok();
                     expect(code).to.be(0);
                     expect(data).to.equal('foo\nbar\\\nbaz');
@@ -236,7 +236,7 @@ extension\');', { mode: parseInt('0777', 8) });
                 });
             });
 
-            it('should handle arguments that contain shell special chars', function (next) {
+            it('should handle arguments that contain shell special chars', (next) => {
                 buffered(method, 'node', [
                     __dirname + '/fixtures/echo',
                     'foo',
@@ -252,7 +252,7 @@ extension\');', { mode: parseInt('0777', 8) });
                     'foo',
                     ', ',
                     'foo',
-                ], function (err, data, code) {
+                ], (err, data, code) => {
                     expect(err).to.not.be.ok();
                     expect(code).to.be(0);
                     expect(data).to.equal('foo\n()\nfoo\n%!\nfoo\n^<\nfoo\n>&\nfoo\n|;\nfoo\n, \nfoo');
@@ -261,50 +261,45 @@ extension\');', { mode: parseInt('0777', 8) });
                 });
             });
 
-            it('should handle special arguments when using echo', function (next) {
-                buffered(method, 'echo', ['foo\\"foo\\foo&bar"foo\'bar'], function (err, data, code) {
+            it('should handle escaping of quotes followed by special meta chars', (next) => {
+                const arg = '"(foo|bar>baz|foz)"';
+
+                buffered(method, 'node', [
+                    __dirname + '/fixtures/echo',
+                    arg,
+                ], (err, data, code) => {
                     expect(err).to.not.be.ok();
                     expect(code).to.be(0);
-                    expect(data.trim()).to.equal('foo\\"foo\\foo&bar"foo\'bar');
+                    expect(arg).to.equal(arg);
 
-                    buffered(method, 'echo', [
-                        'foo',
-                        '()',
-                        'foo',
-                        '%!',
-                        'foo',
-                        '^<',
-                        'foo',
-                        '>&',
-                        'foo',
-                        '|;',
-                        'foo',
-                        ', ',
-                        'foo',
-                    ], function (err, data, code) {
-                        expect(err).to.not.be.ok();
-                        expect(code).to.be(0);
-                        expect(data.trim()).to.equal('foo () foo %! foo ^< foo >& foo |; foo ,  foo');
+                    next();
+                });
+            });
 
-                        next();
-                    });
+            it('should handle commands with names of environment variables', (next) => {
+                buffered(method, __dirname + '/fixtures/%CD%', (err, data, code) => {
+                    expect(err).to.not.be.ok();
+                    expect(code).to.be(0);
+                    expect(data.trim()).to.equal('special');
+
+                    next();
                 });
             });
 
-            it('should handle optional args correctly', function (next) {
-                buffered(method, __dirname + '/fixtures/foo', function (err, data, code) {
+            it('should handle optional args correctly', (next) => {
+                buffered(method, __dirname + '/fixtures/foo', (err, data, code) => {
                     expect(err).to.not.be.ok();
                     expect(code).to.be(0);
 
                     buffered(method, __dirname + '/fixtures/foo', {
                         stdio: ['pipe', 'pipe', 'pipe'],
-                    }, function (err, data, code) {
+                    }, (err, data, code) => {
                         expect(err).to.not.be.ok();
                         expect(code).to.be(0);
 
                         buffered(method, __dirname + '/fixtures/foo', null, {
                             stdio: ['pipe', 'pipe', 'pipe'],
-                        }, function (err, data, code) {
+                        }, (err, data, code) => {
                             expect(err).to.not.be.ok();
                             expect(code).to.be(0);
 
@@ -314,11 +309,11 @@ extension\');', { mode: parseInt('0777', 8) });
                 });
             });
 
-            it('should not mutate args nor options', function (next) {
-                var args = [];
-                var options = {};
+            it('should not mutate args nor options', (next) => {
+                const args = [];
+                const options = {};
 
-                buffered(method, __dirname + '/fixtures/foo', function (err, data, code) {
+                buffered(method, __dirname + '/fixtures/foo', options, (err, data, code) => {
                     expect(err).to.not.be.ok();
                     expect(code).to.be(0);
 
@@ -329,8 +324,8 @@ extension\');', { mode: parseInt('0777', 8) });
                 });
             });
 
-            it('should give correct exit code', function (next) {
-                buffered(method, 'node', [__dirname + '/fixtures/exit'], function (err, data, code) {
+            it('should give correct exit code', (next) => {
+                buffered(method, 'node', [__dirname + '/fixtures/exit'], (err, data, code) => {
                     expect(err).to.not.be.ok();
                     expect(code).to.be(25);
 
@@ -338,8 +333,8 @@ extension\');', { mode: parseInt('0777', 8) });
                 });
             });
 
-            it('should work with a relative command', function (next) {
-                buffered(method, path.relative(process.cwd(), __dirname + '/fixtures/foo'), function (err, data, code) {
+            it('should work with a relative command', (next) => {
+                buffered(method, path.relative(process.cwd(), __dirname + '/fixtures/foo'), (err, data, code) => {
                     expect(err).to.not.be.ok();
                     expect(code).to.be(0);
                     expect(data.trim()).to.equal('foo');
@@ -348,7 +343,7 @@ extension\');', { mode: parseInt('0777', 8) });
                         return next();
                     }
 
-                    buffered(method, path.relative(process.cwd(), __dirname + '/fixtures/foo.bat'), function (err, data, code) {
+                    buffered(method, path.relative(process.cwd(), __dirname + '/fixtures/foo.bat'), (err, data, code) => {
                         expect(err).to.not.be.ok();
                         expect(code).to.be(0);
                         expect(data.trim()).to.equal('foo');
@@ -359,13 +354,12 @@ extension\');', { mode: parseInt('0777', 8) });
             });
 
             it('should emit "error" and "close" if command does not exist', function (next) {
-                var errors;
-                var spawned = spawn[method]('somecommandthatwillneverexist');
+                const spawned = spawn[method]('somecommandthatwillneverexist');
 
                 this.timeout(5000);
 
                 function assertError(err) {
-                    var syscall = method === 'sync' ? 'spawnSync' : 'spawn';
+                    const syscall = method === 'sync' ? 'spawnSync' : 'spawn';
 
                     expect(err).to.be.an(Error);
                     expect(err.message).to.contain(syscall);
@@ -378,21 +372,21 @@ extension\');', { mode: parseInt('0777', 8) });
                 }
 
                 if (method === 'spawn') {
-                    errors = [];
+                    const errors = [];
 
                     spawned
-                    .on('error', function (err) {
+                    .on('error', (err) => {
                         errors.push(err);
                     })
-                    .on('exit', function () {
+                    .on('exit', () => {
                         spawned.removeAllListeners();
                         next(new Error('Should not emit exit'));
                     })
-                    .on('close', function (code, signal) {
+                    .on('close', (code, signal) => {
                         expect(code).to.not.be(0);
                         expect(signal).to.be(null);
 
-                        setTimeout(function () {
+                        setTimeout(() => {
                             expect(errors).to.have.length(1);
                             assertError(errors[0]);
 
@@ -406,23 +400,23 @@ extension\');', { mode: parseInt('0777', 8) });
             });
 
             it('should NOT emit "error" if shebang command does not exist', function (next) {
-                var spawned = spawn[method](__dirname + '/fixtures/shebang_enoent');
-                var exited;
-                var timeout;
+                const spawned = spawn[method](__dirname + '/fixtures/shebang_enoent');
+                let exited;
+                let timeout;
 
                 this.timeout(5000);
 
                 if (method === 'spawn') {
                     spawned
-                    .on('error', function () {
+                    .on('error', () => {
                         spawned.removeAllListeners();
                         clearTimeout(timeout);
                         next(new Error('Should not emit error'));
                     })
-                    .on('exit', function () {
+                    .on('exit', () => {
                         exited = true;
                     })
-                    .on('close', function (code, signal) {
+                    .on('close', (code, signal) => {
                         expect(code).to.not.be(0);
                         expect(signal).to.be(null);
                         expect(exited).to.be(true);
@@ -436,23 +430,23 @@ extension\');', { mode: parseInt('0777', 8) });
             });
 
             it('should NOT emit "error" if the command actual exists but exited with 1', function (next) {
-                var spawned = spawn[method](__dirname + '/fixtures/exit1');
-                var exited;
-                var timeout;
+                const spawned = spawn[method](__dirname + '/fixtures/exit1');
+                let exited;
+                let timeout;
 
                 this.timeout(5000);
 
                 if (method === 'spawn') {
                     spawned
-                    .on('error', function () {
+                    .on('error', () => {
                         spawned.removeAllListeners();
                         clearTimeout(timeout);
                         next(new Error('Should not emit error'));
                     })
-                    .on('exit', function () {
+                    .on('exit', () => {
                         exited = true;
                     })
-                    .on('close', function (code, signal) {
+                    .on('close', (code, signal) => {
                         expect(code).to.not.be(0);
                         expect(signal).to.be(null);
                         expect(exited).to.be(true);
@@ -466,63 +460,36 @@ extension\');', { mode: parseInt('0777', 8) });
             });
 
             if (isWin) {
-                it('should use nodejs\' spawn when option.shell is specified', function (next) {
-                    buffered(method, 'echo', ['%RANDOM%'], { shell: true }, function (err, data, code) {
+                it('should use nodejs\' spawn when options.shell is specified', (next) => {
+                    buffered(method, 'echo', ['%RANDOM%'], { shell: true }, (err, data, code) => {
                         expect(err).to.not.be.ok();
                         expect(code).to.be(0);
                         expect(data.trim()).to.match(/\d+/);
 
-                        buffered(method, 'echo', ['%RANDOM%'], { shell: false }, function (err, data) {
-                            // In some windows versions, the echo exists outside the shell as echo.exe so we must account for that here
-                            if (err) {
-                                expect(err).to.be.an(Error);
-                                expect(err.message).to.contain('ENOENT');
-                            } else {
-                                expect(data.trim()).to.equal('%RANDOM%');
-                            }
-
-                            next();
-                        });
+                        next();
                     });
                 });
             } else {
-                it('should use nodejs\' spawn when option.shell is specified', function (next) {
-                    buffered(method, 'echo', ['hello &&', 'echo there'], { shell: true }, function (err, data, code) {
+                it('should use nodejs\' spawn when options.shell is specified', (next) => {
+                    buffered(method, 'echo', ['hello &&', 'echo there'], { shell: true }, (err, data, code) => {
                         expect(err).to.not.be.ok();
                         expect(code).to.be(0);
                         expect(data.trim()).to.equal('hello\nthere');
 
-                        buffered(method, 'echo', ['hello &&', 'echo there'], { shell: false }, function (err, data) {
-                            expect(err).to.not.be.ok();
-                            expect(code).to.be(0);
-                            expect(data.trim()).to.equal('hello && echo there');
-
-                            next();
-                        });
+                        next();
                     });
                 });
             }
 
             if (isWin) {
-                if (hasEmptyArgumentBug) {
-                    it('should spawn a shell for a .exe on old Node', function (next) {
-                        buffered(method, __dirname + '/fixtures/win-ppid.js', function (err, data, code) {
-                            expect(err).to.not.be.ok();
-                            expect(code).to.be(0);
-                            expect(data.trim()).to.not.equal('' + process.pid);
-                            next();
-                        });
-                    });
-                } else {
-                    it('should NOT spawn a shell for a .exe', function (next) {
-                        buffered(method, __dirname + '/fixtures/win-ppid.js', function (err, data, code) {
-                            expect(err).to.not.be.ok();
-                            expect(code).to.be(0);
-                            expect(data.trim()).to.equal('' + process.pid);
-                            next();
-                        });
+                it('should NOT spawn a shell for a .exe', (next) => {
+                    buffered(method, __dirname + '/fixtures/win-ppid.js', (err, data, code) => {
+                        expect(err).to.not.be.ok();
+                        expect(code).to.be(0);
+                        expect(data.trim()).to.equal('' + process.pid);
+                        next();
                     });
-                }
+                });
             }
         });
     });
diff --git a/test/util/buffered.js b/test/util/buffered.js
index 2c0ce59..7f225e4 100644
--- a/test/util/buffered.js
+++ b/test/util/buffered.js
@@ -1,14 +1,9 @@
 'use strict';
 
-var spawn = require('../../index');
-var once = require('once');
+const spawn = require('../../index');
+const once = require('once');
 
 function buffered(method, command, args, options, callback) {
-    var cp;
-    var stdout;
-    var stderr;
-    var results;
-
     if (typeof options === 'function') {
         callback = options;
         options = null;
@@ -20,26 +15,29 @@ function buffered(method, command, args, options, callback) {
     }
 
     if (method === 'sync') {
-        results = spawn.sync(command, args, options);
+        const results = spawn.sync(command, args, options);
+
         callback(results.error, results.stdout ? results.stdout.toString() : null, results.status);
     } else {
-        cp = spawn(command, args, options);
-        stdout = stderr = null;
+        const cp = spawn(command, args, options);
+        let stdout = null;
+        let stderr = null;
+
         callback = once(callback);
 
-        cp.stdout && cp.stdout.on('data', function (buffer) {
+        cp.stdout && cp.stdout.on('data', (buffer) => {
             stdout = stdout || '';
             stdout += buffer.toString();
         });
 
-        cp.stderr && cp.stderr.on('data', function (buffer) {
+        cp.stderr && cp.stderr.on('data', (buffer) => {
             stderr = stderr || '';
             stderr += buffer.toString();
         });
 
         cp.on('error', callback);
 
-        cp.on('close', function (code) {
+        cp.on('close', (code) => {
             code !== 0 && stderr && console.warn(stderr);
             callback(null, stdout, code);
         });