diff --git a/lib/_stream_writable.js b/lib/_stream_writable.js
index af199956062d67..ced41e9ab9562f 100644
--- a/lib/_stream_writable.js
+++ b/lib/_stream_writable.js
@@ -190,7 +190,7 @@ function WritableState(options, stream, isDuplex) {
 }
 
 WritableState.prototype.getBuffer = function getBuffer() {
-  var current = this.bufferedRequest;
+  let current = this.bufferedRequest;
   const out = [];
   while (current) {
     out.push(current);
@@ -201,7 +201,7 @@ WritableState.prototype.getBuffer = function getBuffer() {
 
 // Test _writableState for inheritance to account for Duplex streams,
 // whose prototype chain only points to Readable.
-var realHasInstance;
+let realHasInstance;
 if (typeof Symbol === 'function' && SymbolHasInstance) {
   realHasInstance = FunctionPrototype[SymbolHasInstance];
   ObjectDefineProperty(Writable, SymbolHasInstance, {
@@ -351,7 +351,7 @@ function writeOrBuffer(stream, state, chunk, encoding, cb) {
     state.needDrain = true;
 
   if (state.writing || state.corked || state.errored) {
-    var last = state.lastBufferedRequest;
+    const last = state.lastBufferedRequest;
     state.lastBufferedRequest = {
       chunk,
       encoding,
@@ -424,7 +424,7 @@ function onwrite(stream, er) {
     }
   } else {
     // Check if we're actually ready to finish, but don't emit yet
-    var finished = needFinish(state) || stream.destroyed;
+    const finished = needFinish(state) || stream.destroyed;
 
     if (!finished &&
         !state.corked &&
@@ -495,17 +495,17 @@ function errorBuffer(state, err) {
 // If there's something in the buffer waiting, then process it
 function clearBuffer(stream, state) {
   state.bufferProcessing = true;
-  var entry = state.bufferedRequest;
+  let entry = state.bufferedRequest;
 
   if (stream._writev && entry && entry.next) {
     // Fast case, write everything using _writev()
-    var l = state.bufferedRequestCount;
-    var buffer = new Array(l);
-    var holder = state.corkedRequestsFree;
+    const l = state.bufferedRequestCount;
+    const buffer = new Array(l);
+    const holder = state.corkedRequestsFree;
     holder.entry = entry;
 
-    var count = 0;
-    var allBuffers = true;
+    let count = 0;
+    let allBuffers = true;
     while (entry) {
       buffer[count] = entry;
       if (entry.encoding !== 'buffer')
@@ -525,7 +525,7 @@ function clearBuffer(stream, state) {
       state.corkedRequestsFree = holder.next;
       holder.next = null;
     } else {
-      var corkReq = { next: null, entry: null, finish: undefined };
+      const corkReq = { next: null, entry: null, finish: undefined };
       corkReq.finish = onCorkedFinish.bind(undefined, corkReq, state);
       state.corkedRequestsFree = corkReq;
     }
@@ -533,10 +533,10 @@ function clearBuffer(stream, state) {
   } else {
     // Slow case, write chunks one-by-one
     while (entry) {
-      var chunk = entry.chunk;
-      var encoding = entry.encoding;
-      var cb = entry.callback;
-      var len = state.objectMode ? 1 : chunk.length;
+      const chunk = entry.chunk;
+      const encoding = entry.encoding;
+      const cb = entry.callback;
+      const len = state.objectMode ? 1 : chunk.length;
 
       doWrite(stream, state, false, len, chunk, encoding, cb);
       entry = entry.next;
@@ -692,10 +692,10 @@ function endWritable(stream, state, cb) {
 }
 
 function onCorkedFinish(corkReq, state, err) {
-  var entry = corkReq.entry;
+  let entry = corkReq.entry;
   corkReq.entry = null;
   while (entry) {
-    var cb = entry.callback;
+    const cb = entry.callback;
     state.pendingcb--;
     cb(err);
     entry = entry.next;