diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 43b69f8..8033855 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -8,7 +8,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [10.x, 12.x, 13.x]
+        node-version: [10.x, 12.x, 13.x, 14.x, 15.x]
 
     steps:
       - uses: actions/checkout@v1
diff --git a/abstractTest.js b/abstractTest.js
index 6f57447..0a7f24f 100644
--- a/abstractTest.js
+++ b/abstractTest.js
@@ -2,8 +2,8 @@
 'use strict'
 
 module.exports = function abstractTests (opts) {
-  var builder = opts.builder
-  var test = opts.test
+  const builder = opts.builder
+  const test = opts.test
 
   test('support on and emit', function (t) {
     t.plan(4)
@@ -93,7 +93,7 @@ module.exports = function abstractTests (opts) {
       topic: 'hello world',
       payload: { my: 'message' }
     }
-    var toRemoveCalled = false
+    let toRemoveCalled = false
 
     function toRemove (message, cb) {
       toRemoveCalled = true
@@ -395,7 +395,7 @@ module.exports = function abstractTests (opts) {
 
   test('close support', function (t) {
     const e = builder()
-    var check = false
+    let check = false
 
     t.notOk(e.closed, 'must have a false closed property')
 
@@ -425,8 +425,8 @@ module.exports = function abstractTests (opts) {
       topic: 'hello/world',
       payload: { my: 'message' }
     }
-    var firstCalled = false
-    var secondCalled = false
+    let firstCalled = false
+    let secondCalled = false
 
     e.on('hello/#', function (message, cb) {
       t.notOk(firstCalled, 'first subscriber must only be called once')
@@ -453,8 +453,8 @@ module.exports = function abstractTests (opts) {
       topic: 'hello/my/world',
       payload: { my: 'message' }
     }
-    var firstCalled = false
-    var secondCalled = false
+    let firstCalled = false
+    let secondCalled = false
 
     e.on('hello/#', function (message, cb) {
       t.notOk(firstCalled, 'first subscriber must only be called once')
@@ -500,10 +500,10 @@ module.exports = function abstractTests (opts) {
     const total = 10000
     const topic = 'test'
 
-    var received = 0
+    let received = 0
 
     e.on(topic, function (msg, cb) {
-      var fail = false
+      let fail = false
       if (received !== msg.payload) {
         t.fail(`leak detected. Count: ${received} - Payload: ${msg.payload}`)
         fail = true
diff --git a/bench.js b/bench.js
index e2edfc6..cfb9a34 100644
--- a/bench.js
+++ b/bench.js
@@ -3,8 +3,8 @@
 const mqemitter = require('./')
 const emitter = mqemitter({ concurrency: 10 })
 const total = 1000000
-var written = 0
-var received = 0
+let written = 0
+let received = 0
 const timerKey = 'time for sending ' + total + ' messages'
 
 function write () {
diff --git a/package.json b/package.json
index 610345c..1daf9ad 100644
--- a/package.json
+++ b/package.json
@@ -7,7 +7,7 @@
   "scripts": {
     "lint": "npm run lint:standard && npm run lint:typescript && npm run lint:markdown",
     "lint:standard": "standard --verbose | snazzy",
-    "lint:typescript": "standard --parser @typescript-eslint/parser --plugin @typescript-eslint/eslint-plugin test/types/*.ts mqemitter.d.ts",
+    "lint:typescript": "standard --parser @typescript-eslint/parser --plugin @typescript-eslint/eslint-plugin test/types/*.ts types/mqemitter.d.ts",
     "lint:markdown": "markdownlint README.md",
     "unit": "tape test/*.js",
     "unit:report": "nyc --reporter=html --reporter=cobertura --reporter=text tape test/*.js",
@@ -51,7 +51,7 @@
     "nyc": "^15.0.0",
     "pre-commit": "^1.2.2",
     "snazzy": "^9.0.0",
-    "standard": "^15.0.0",
+    "standard": "^16.0.0",
     "tape": "^5.0.1",
     "tsd": "^0.14.0",
     "typescript": "^4.0.2"
diff --git a/test/test.js b/test/test.js
index f620d85..7e8b567 100644
--- a/test/test.js
+++ b/test/test.js
@@ -12,7 +12,7 @@ test('queue concurrency', function (t) {
   t.plan(3)
 
   const e = mq({ concurrency: 1 })
-  var completed1 = false
+  let completed1 = false
 
   t.equal(e.concurrency, 1)
 
@@ -54,7 +54,7 @@ test('queue concurrency with overlapping subscriptions', function (t) {
   t.plan(3)
 
   const e = mq({ concurrency: 1 })
-  var completed1 = false
+  let completed1 = false
 
   t.equal(e.concurrency, 1)
 
diff --git a/test/types/index.ts b/test/types/index.ts
index eb3c9c3..98457ab 100644
--- a/test/types/index.ts
+++ b/test/types/index.ts
@@ -5,7 +5,7 @@ import MQEmitter, { Message } from '../../types/mqemitter'
 
 const noop = function () {}
 
-var mq = MQEmitter()
+let mq = MQEmitter()
 mq = MQEmitter({
   concurrency: 100
 })