diff --git a/lib/internal/cluster/round_robin_handle.js b/lib/internal/cluster/round_robin_handle.js
index e89a309c79844c..213b72c19f4273 100644
--- a/lib/internal/cluster/round_robin_handle.js
+++ b/lib/internal/cluster/round_robin_handle.js
@@ -1,6 +1,7 @@
 'use strict';
 
 const {
+  ArrayIsArray,
   Boolean,
   Map,
 } = primordials;
@@ -15,7 +16,7 @@ module.exports = RoundRobinHandle;
 function RoundRobinHandle(key, address, port, addressType, fd, flags) {
   this.key = key;
   this.all = new Map();
-  this.free = [];
+  this.free = new Map();
   this.handles = [];
   this.handle = null;
   this.server = net.createServer(assert.fail);
@@ -73,10 +74,7 @@ RoundRobinHandle.prototype.remove = function(worker) {
   if (!existed)
     return false;
 
-  const index = this.free.indexOf(worker);
-
-  if (index !== -1)
-    this.free.splice(index, 1);
+  this.free.delete(worker.id);
 
   if (this.all.size !== 0)
     return false;
@@ -93,21 +91,24 @@ RoundRobinHandle.prototype.remove = function(worker) {
 
 RoundRobinHandle.prototype.distribute = function(err, handle) {
   this.handles.push(handle);
-  const worker = this.free.shift();
+  const [ workerEntry ] = this.free;
 
-  if (worker)
+  if (ArrayIsArray(workerEntry)) {
+    const [ workerId, worker ] = workerEntry;
+    this.free.delete(workerId);
     this.handoff(worker);
+  }
 };
 
 RoundRobinHandle.prototype.handoff = function(worker) {
-  if (this.all.has(worker.id) === false) {
+  if (!this.all.has(worker.id)) {
     return;  // Worker is closing (or has closed) the server.
   }
 
   const handle = this.handles.shift();
 
   if (handle === undefined) {
-    this.free.push(worker);  // Add to ready queue again.
+    this.free.set(worker.id, worker);  // Add to ready queue again.
     return;
   }
 
diff --git a/lib/internal/cluster/shared_handle.js b/lib/internal/cluster/shared_handle.js
index 088798597382f8..20c028ce313d40 100644
--- a/lib/internal/cluster/shared_handle.js
+++ b/lib/internal/cluster/shared_handle.js
@@ -1,4 +1,5 @@
 'use strict';
+const { Map } = primordials;
 const assert = require('internal/assert');
 const dgram = require('internal/dgram');
 const net = require('net');
@@ -7,7 +8,7 @@ module.exports = SharedHandle;
 
 function SharedHandle(key, address, port, addressType, fd, flags) {
   this.key = key;
-  this.workers = [];
+  this.workers = new Map();
   this.handle = null;
   this.errno = 0;
 
@@ -24,20 +25,18 @@ function SharedHandle(key, address, port, addressType, fd, flags) {
 }
 
 SharedHandle.prototype.add = function(worker, send) {
-  assert(!this.workers.includes(worker));
-  this.workers.push(worker);
+  assert(!this.workers.has(worker.id));
+  this.workers.set(worker.id, worker);
   send(this.errno, null, this.handle);
 };
 
 SharedHandle.prototype.remove = function(worker) {
-  const index = this.workers.indexOf(worker);
-
-  if (index === -1)
-    return false; // The worker wasn't sharing this handle.
+  if (!this.workers.has(worker.id))
+    return false;
 
-  this.workers.splice(index, 1);
+  this.workers.delete(worker.id);
 
-  if (this.workers.length !== 0)
+  if (this.workers.size !== 0)
     return false;
 
   this.handle.close();