diff --git a/lib/_http_outgoing.js b/lib/_http_outgoing.js
index 36d3054eab0663..c1f277da3fff57 100644
--- a/lib/_http_outgoing.js
+++ b/lib/_http_outgoing.js
@@ -168,7 +168,7 @@ ObjectDefineProperty(OutgoingMessage.prototype, '_headers', {
       const keys = ObjectKeys(val);
       // Retain for(;;) loop for performance reasons
       // Refs: https://github.com/nodejs/node/pull/30958
-      for (var i = 0; i < keys.length; ++i) {
+      for (let i = 0; i < keys.length; ++i) {
         const name = keys[i];
         headers[name.toLowerCase()] = [name, val[name]];
       }
@@ -193,7 +193,7 @@ ObjectDefineProperty(OutgoingMessage.prototype, '_headerNames', {
       const keys = ObjectKeys(headers);
       // Retain for(;;) loop for performance reasons
       // Refs: https://github.com/nodejs/node/pull/30958
-      for (var i = 0; i < keys.length; ++i) {
+      for (let i = 0; i < keys.length; ++i) {
         const key = keys[i];
         const val = headers[key][0];
         out[key] = val;
@@ -210,7 +210,7 @@ ObjectDefineProperty(OutgoingMessage.prototype, '_headerNames', {
       const keys = ObjectKeys(val);
       // Retain for(;;) loop for performance reasons
       // Refs: https://github.com/nodejs/node/pull/30958
-      for (var i = 0; i < keys.length; ++i) {
+      for (let i = 0; i < keys.length; ++i) {
         const header = headers[keys[i]];
         if (header)
           header[0] = val[keys[i]];
@@ -232,7 +232,7 @@ OutgoingMessage.prototype._renderHeaders = function _renderHeaders() {
     const keys = ObjectKeys(headersMap);
     // Retain for(;;) loop for performance reasons
     // Refs: https://github.com/nodejs/node/pull/30958
-    for (var i = 0, l = keys.length; i < l; i++) {
+    for (let i = 0, l = keys.length; i < l; i++) {
       const key = keys[i];
       headers[headersMap[key][0]] = headersMap[key][1];
     }
@@ -297,7 +297,7 @@ OutgoingMessage.prototype._send = function _send(data, encoding, callback) {
         (encoding === 'utf8' || encoding === 'latin1' || !encoding)) {
       data = this._header + data;
     } else {
-      var header = this._header;
+      const header = this._header;
       if (this.outputData.length === 0) {
         this.outputData = [{
           data: header,
@@ -468,7 +468,7 @@ function processHeader(self, state, key, value, validate) {
     if (value.length < 2 || !isCookieField(key)) {
       // Retain for(;;) loop for performance reasons
       // Refs: https://github.com/nodejs/node/pull/30958
-      for (var i = 0; i < value.length; i++)
+      for (let i = 0; i < value.length; i++)
         storeHeader(self, state, key, value[i], validate);
       return;
     }
@@ -571,7 +571,7 @@ OutgoingMessage.prototype.getHeaders = function getHeaders() {
     const keys = ObjectKeys(headers);
     // Retain for(;;) loop for performance reasons
     // Refs: https://github.com/nodejs/node/pull/30958
-    for (var i = 0; i < keys.length; ++i) {
+    for (let i = 0; i < keys.length; ++i) {
       const key = keys[i];
       const val = headers[key][1];
       ret[key] = val;
@@ -676,8 +676,9 @@ function write_(msg, chunk, encoding, callback, fromEnd) {
     process.nextTick(connectionCorkNT, msg.socket);
   }
 
-  var len, ret;
+  let ret;
   if (msg.chunkedEncoding && chunk.length !== 0) {
+    let len;
     if (typeof chunk === 'string')
       len = Buffer.byteLength(chunk, encoding);
     else
@@ -711,11 +712,11 @@ OutgoingMessage.prototype.addTrailers = function addTrailers(headers) {
   this._trailer = '';
   const keys = ObjectKeys(headers);
   const isArray = ArrayIsArray(headers);
-  var field, value;
   // Retain for(;;) loop for performance reasons
   // Refs: https://github.com/nodejs/node/pull/30958
-  for (var i = 0, l = keys.length; i < l; i++) {
-    var key = keys[i];
+  for (let i = 0, l = keys.length; i < l; i++) {
+    let field, value;
+    const key = keys[i];
     if (isArray) {
       field = headers[key][0];
       value = headers[key][1];
@@ -839,11 +840,10 @@ OutgoingMessage.prototype._finish = function _finish() {
 // to attempt to flush any pending messages out to the socket.
 OutgoingMessage.prototype._flush = function _flush() {
   const socket = this.socket;
-  var ret;
 
   if (socket && socket.writable) {
     // There might be remaining data in this.output; write it out
-    ret = this._flushOutput(socket);
+    const ret = this._flushOutput(socket);
 
     if (this.finished) {
       // This is a queue to the server or client to bring in the next this.
@@ -870,7 +870,7 @@ OutgoingMessage.prototype._flushOutput = function _flushOutput(socket) {
   let ret;
   // Retain for(;;) loop for performance reasons
   // Refs: https://github.com/nodejs/node/pull/30958
-  for (var i = 0; i < outputLength; i++) {
+  for (let i = 0; i < outputLength; i++) {
     const { data, encoding, callback } = outputData[i];
     ret = socket.write(data, encoding, callback);
   }