diff --git a/lib/internal/child_process.js b/lib/internal/child_process.js
index 9e13650fa3d56a..2d4aff982b05a0 100644
--- a/lib/internal/child_process.js
+++ b/lib/internal/child_process.js
@@ -103,8 +103,8 @@ const handleConversion = {
         // The worker should keep track of the socket
         message.key = socket.server._connectionKey;
 
-        var firstTime = !this.channel.sockets.send[message.key];
-        var socketList = getSocketList('send', this, message.key);
+        const firstTime = !this.channel.sockets.send[message.key];
+        const socketList = getSocketList('send', this, message.key);
 
         // The server should no longer expose a .connection property
         // and when asked to close it should query the socket status from
@@ -171,7 +171,7 @@ const handleConversion = {
       if (message.key) {
 
         // Add socket to connections list
-        var socketList = getSocketList('got', this, message.key);
+        const socketList = getSocketList('got', this, message.key);
         socketList.add({
           socket: socket
         });
@@ -258,7 +258,7 @@ function ChildProcess() {
     this._handle = null;
 
     if (exitCode < 0) {
-      var syscall = this.spawnfile ? 'spawn ' + this.spawnfile : 'spawn';
+      const syscall = this.spawnfile ? 'spawn ' + this.spawnfile : 'spawn';
       const err = errnoException(exitCode, syscall);
 
       if (this.spawnfile)
@@ -290,7 +290,7 @@ function flushStdio(subprocess) {
 
   if (stdio == null) return;
 
-  for (var i = 0; i < stdio.length; i++) {
+  for (let i = 0; i < stdio.length; i++) {
     const stream = stdio[i];
     // TODO(addaleax): This doesn't necessarily account for all the ways in
     // which data can be read from a stream, e.g. being consumed on the
@@ -471,7 +471,7 @@ ChildProcess.prototype.kill = function(sig) {
     convertToValidSignal(sig === undefined ? 'SIGTERM' : sig);
 
   if (this._handle) {
-    var err = this._handle.kill(signal);
+    const err = this._handle.kill(signal);
     if (err === 0) {
       /* Success. */
       this.killed = true;
@@ -611,7 +611,7 @@ function setupChannel(target, channel, serializationMode) {
       }
 
       assert(Array.isArray(target._handleQueue));
-      var queue = target._handleQueue;
+      const queue = target._handleQueue;
       target._handleQueue = null;
 
       if (target._pendingMessage) {
@@ -621,8 +621,8 @@ function setupChannel(target, channel, serializationMode) {
                      target._pendingMessage.callback);
       }
 
-      for (var i = 0; i < queue.length; i++) {
-        var args = queue[i];
+      for (let i = 0; i < queue.length; i++) {
+        const args = queue[i];
         target._send(args.message, args.handle, args.options, args.callback);
       }
 
@@ -854,7 +854,7 @@ function setupChannel(target, channel, serializationMode) {
     if (this._pendingMessage)
       closePendingHandle(this);
 
-    var fired = false;
+    let fired = false;
     function finish() {
       if (fired) return;
       fired = true;
@@ -903,8 +903,8 @@ function isInternal(message) {
 function nop() { }
 
 function getValidStdio(stdio, sync) {
-  var ipc;
-  var ipcFd;
+  let ipc;
+  let ipcFd;
 
   // Replace shortcut with an array
   if (typeof stdio === 'string') {
@@ -923,7 +923,7 @@ function getValidStdio(stdio, sync) {
   // (i.e. PipeWraps or fds)
   stdio = stdio.reduce((acc, stdio, i) => {
     function cleanup() {
-      for (var i = 0; i < acc.length; i++) {
+      for (let i = 0; i < acc.length; i++) {
         if ((acc[i].type === 'pipe' || acc[i].type === 'ipc') && acc[i].handle)
           acc[i].handle.close();
       }
@@ -937,7 +937,7 @@ function getValidStdio(stdio, sync) {
     if (stdio === 'ignore') {
       acc.push({ type: 'ignore' });
     } else if (stdio === 'pipe' || (typeof stdio === 'number' && stdio < 0)) {
-      var a = {
+      const a = {
         type: 'pipe',
         readable: i === 0,
         writable: i !== 0
@@ -977,7 +977,7 @@ function getValidStdio(stdio, sync) {
       });
     } else if (getHandleWrapType(stdio) || getHandleWrapType(stdio.handle) ||
                getHandleWrapType(stdio._handle)) {
-      var handle = getHandleWrapType(stdio) ?
+      const handle = getHandleWrapType(stdio) ?
         stdio :
         getHandleWrapType(stdio.handle) ? stdio.handle : stdio._handle;
 
@@ -1007,9 +1007,9 @@ function getValidStdio(stdio, sync) {
 
 function getSocketList(type, worker, key) {
   const sockets = worker.channel.sockets[type];
-  var socketList = sockets[key];
+  let socketList = sockets[key];
   if (!socketList) {
-    var Construct = type === 'send' ? SocketListSend : SocketListReceive;
+    const Construct = type === 'send' ? SocketListSend : SocketListReceive;
     socketList = sockets[key] = new Construct(worker, key);
   }
   return socketList;
@@ -1028,7 +1028,7 @@ function spawnSync(options) {
   const result = spawn_sync.spawn(options);
 
   if (result.output && options.encoding && options.encoding !== 'buffer') {
-    for (var i = 0; i < result.output.length; i++) {
+    for (let i = 0; i < result.output.length; i++) {
       if (!result.output[i])
         continue;
       result.output[i] = result.output[i].toString(options.encoding);