diff --git a/lib/aggregate.js b/lib/aggregate.js
index 4d93251855f..746d7620b6d 100644
--- a/lib/aggregate.js
+++ b/lib/aggregate.js
@@ -11,7 +11,6 @@ const getConstructorName = require('./helpers/getConstructorName');
 const prepareDiscriminatorPipeline = require('./helpers/aggregate/prepareDiscriminatorPipeline');
 const promiseOrCallback = require('./helpers/promiseOrCallback');
 const stringifyFunctionOperators = require('./helpers/aggregate/stringifyFunctionOperators');
-const util = require('util');
 const utils = require('./utils');
 const read = Query.prototype.read;
 const readConcern = Query.prototype.readConcern;
@@ -55,7 +54,7 @@ function Aggregate(pipeline, model) {
   this._model = model;
   this.options = {};
 
-  if (arguments.length === 1 && util.isArray(pipeline)) {
+  if (arguments.length === 1 && Array.isArray(pipeline)) {
     this.append.apply(this, pipeline);
   }
 }
@@ -138,7 +137,7 @@ Aggregate.prototype.model = function(model) {
  */
 
 Aggregate.prototype.append = function() {
-  const args = (arguments.length === 1 && util.isArray(arguments[0]))
+  const args = (arguments.length === 1 && Array.isArray(arguments[0]))
     ? arguments[0]
     : utils.args(arguments);
 
@@ -176,7 +175,7 @@ Aggregate.prototype.append = function() {
  */
 Aggregate.prototype.addFields = function(arg) {
   const fields = {};
-  if (typeof arg === 'object' && !util.isArray(arg)) {
+  if (typeof arg === 'object' && !Array.isArray(arg)) {
     Object.keys(arg).forEach(function(field) {
       fields[field] = arg[field];
     });
@@ -221,7 +220,7 @@ Aggregate.prototype.addFields = function(arg) {
 Aggregate.prototype.project = function(arg) {
   const fields = {};
 
-  if (typeof arg === 'object' && !util.isArray(arg)) {
+  if (typeof arg === 'object' && !Array.isArray(arg)) {
     Object.keys(arg).forEach(function(field) {
       fields[field] = arg[field];
     });