diff --git a/lib/internal/cluster/master.js b/lib/internal/cluster/master.js
index a881021c5e01ce..785d4c5913320a 100644
--- a/lib/internal/cluster/master.js
+++ b/lib/internal/cluster/master.js
@@ -29,12 +29,12 @@ cluster.settings = {};
 cluster.SCHED_NONE = SCHED_NONE;  // Leave it to the operating system.
 cluster.SCHED_RR = SCHED_RR;      // Master distributes connections.
 
-var ids = 0;
-var debugPortOffset = 1;
-var initialized = false;
+let ids = 0;
+let debugPortOffset = 1;
+let initialized = false;
 
 // XXX(bnoordhuis) Fold cluster.schedulingPolicy into cluster.settings?
-var schedulingPolicy = {
+let schedulingPolicy = {
   'none': SCHED_NONE,
   'rr': SCHED_RR
 }[process.env.NODE_CLUSTER_SCHED_POLICY];
@@ -270,7 +270,7 @@ function queryServer(worker, message) {
 
   const key = `${message.address}:${message.port}:${message.addressType}:` +
               `${message.fd}:${message.index}`;
-  var handle = handles.get(key);
+  let handle = handles.get(key);
 
   if (handle === undefined) {
     let address = message.address;
@@ -285,7 +285,7 @@ function queryServer(worker, message) {
         address = message.address;
     }
 
-    var constructor = RoundRobinHandle;
+    let constructor = RoundRobinHandle;
     // UDP is exempt from round-robin connection balancing for what should
     // be obvious reasons: it's connectionless. There is nothing to send to
     // the workers except raw datagrams and that's pointless.