diff --git a/lib/_stream_duplex.js b/lib/_stream_duplex.js
index 572e6da94d8a6a..af2522313f80a2 100644
--- a/lib/_stream_duplex.js
+++ b/lib/_stream_duplex.js
@@ -42,9 +42,7 @@ ObjectSetPrototypeOf(Duplex, Readable);
 
 {
   // Allow the keys array to be GC'ed.
-  const keys = ObjectKeys(Writable.prototype);
-  for (let v = 0; v < keys.length; v++) {
-    const method = keys[v];
+  for (const method of ObjectKeys(Writable.prototype)) {
     if (!Duplex.prototype[method])
       Duplex.prototype[method] = Writable.prototype[method];
   }
diff --git a/lib/_stream_readable.js b/lib/_stream_readable.js
index 5ed86c62b7aed2..d69e5aa5b35f5f 100644
--- a/lib/_stream_readable.js
+++ b/lib/_stream_readable.js
@@ -877,8 +877,8 @@ Readable.prototype.unpipe = function(dest) {
     state.pipes = [];
     state.flowing = false;
 
-    for (var i = 0; i < dests.length; i++)
-      dests[i].emit('unpipe', this, { hasUnpiped: false });
+    for (const dest of dests)
+      dest.emit('unpipe', this, { hasUnpiped: false });
     return this;
   }
 
@@ -1082,8 +1082,8 @@ Readable.prototype.wrap = function(stream) {
   }
 
   // Proxy certain important events.
-  for (var n = 0; n < kProxyEvents.length; n++) {
-    stream.on(kProxyEvents[n], this.emit.bind(this, kProxyEvents[n]));
+  for (const kProxyEvent of kProxyEvents) {
+    stream.on(kProxyEvent, this.emit.bind(this, kProxyEvent));
   }
 
   // When we try to consume some more bytes, simply unpause the