diff --git a/circle.yml b/circle.yml
index d21cf76..58f69ef 100644
--- a/circle.yml
+++ b/circle.yml
@@ -6,5 +6,5 @@ test:
     - mkdir -p $CIRCLE_TEST_REPORTS/unit
   override:
     - npm run test:lint
-    - nvm use 4 && MOCHA_FILE=$CIRCLE_TEST_REPORTS/unit/node4.xml npm run test:unit
-    - nvm use 6 && MOCHA_FILE=$CIRCLE_TEST_REPORTS/unit/node6.xml npm run test:ci
+    - nvm use 6 && MOCHA_FILE=$CIRCLE_TEST_REPORTS/unit/node4.xml npm run test:unit
+    - nvm use 8 && MOCHA_FILE=$CIRCLE_TEST_REPORTS/unit/node6.xml npm run test:ci
diff --git a/package.json b/package.json
index cde3655..49a296f 100644
--- a/package.json
+++ b/package.json
@@ -15,17 +15,18 @@
   ],
   "author": "Tim De Pauw <hi@tmdpw.eu> (https://tmdpw.eu/)",
   "engines": {
-    "node": ">=4"
+    "node": ">=6"
+  },
+  "peerDependencies": {
+    "winston": "^2.3.1"
   },
   "dependencies": {
     "aws-sdk": "^2.58.0",
     "babel-runtime": "^6.23.0",
     "bottleneck": "^1.15.1",
-    "debug": "^2.6.8",
-    "defaults": "^1.0.3",
+    "debug": "^3.1.0",
     "lodash.find": "^4.4.0",
-    "lodash.isempty": "^4.2.1",
-    "winston": "^2.3.1"
+    "lodash.isempty": "^4.2.1"
   },
   "devDependencies": {
     "babel-cli": "^6.24.1",
@@ -34,14 +35,14 @@
     "babel-register": "^6.24.1",
     "chai": "^4.0.2",
     "chai-as-promised": "^7.0.0",
-    "coveralls": "^2.13.1",
+    "coveralls": "^3.0.0",
     "delay": "^2.0.0",
     "in-publish": "^2.0.0",
-    "mocha": "^3.4.2",
+    "mocha": "^4.0.1",
     "mocha-junit-reporter": "^1.13.0",
     "nyc": "^11.0.3",
     "rimraf": "^2.6.1",
-    "sinon": "^2.3.1",
+    "sinon": "^4.1.2",
     "sinon-chai": "^2.10.0",
     "standard": "^10.0.2"
   },
diff --git a/src/cloudwatch-client.js b/src/cloudwatch-client.js
index 467fa3d..489fb45 100644
--- a/src/cloudwatch-client.js
+++ b/src/cloudwatch-client.js
@@ -2,25 +2,26 @@
 
 import _debug from 'debug'
 import AWS from 'aws-sdk'
-import defaults from 'defaults'
 import find from 'lodash.find'
 import CloudWatchEventFormatter from './cloudwatch-event-formatter'
 
 const debug = _debug('winston-aws-cloudwatch:CloudWatchClient')
 
+const DEFAULT_OPTIONS = {
+  awsConfig: null,
+  formatLog: null,
+  formatLogItem: null,
+  createLogGroup: false,
+  createLogStream: false,
+  submissionRetryCount: 1
+}
+
 export default class CloudWatchClient {
   constructor (logGroupName, logStreamName, options) {
     debug('constructor', {logGroupName, logStreamName, options})
     this._logGroupName = logGroupName
     this._logStreamName = logStreamName
-    this._options = defaults(options, {
-      awsConfig: null,
-      formatLog: null,
-      formatLogItem: null,
-      createLogGroup: false,
-      createLogStream: false,
-      submissionRetryCount: 1
-    })
+    this._options = Object.assign({}, DEFAULT_OPTIONS, options)
     this._formatter = new CloudWatchEventFormatter(this._options)
     this._sequenceToken = null
     this._client = new AWS.CloudWatchLogs(this._options.awsConfig)
diff --git a/src/relay.js b/src/relay.js
index 05704a4..ab057a6 100644
--- a/src/relay.js
+++ b/src/relay.js
@@ -2,21 +2,22 @@
 
 import _debug from 'debug'
 import Bottleneck from 'bottleneck'
-import defaults from 'defaults'
 import Queue from './queue'
 import {EventEmitter} from 'events'
 
 const debug = _debug('winston-aws-cloudwatch:Relay')
 
+const DEFAULT_OPTIONS = {
+  submissionInterval: 2000,
+  batchSize: 20
+}
+
 export default class Relay extends EventEmitter {
   constructor (client, options) {
     super()
     debug('constructor', {client, options})
     this._client = client
-    this._options = defaults(options, {
-      submissionInterval: 2000,
-      batchSize: 20
-    })
+    this._options = Object.assign({}, DEFAULT_OPTIONS, options)
     this._limiter = null
     this._queue = null
   }
diff --git a/test/unit/cloudwatch-client.spec.js b/test/unit/cloudwatch-client.spec.js
index 23e6f1c..9b942bc 100644
--- a/test/unit/cloudwatch-client.spec.js
+++ b/test/unit/cloudwatch-client.spec.js
@@ -1,6 +1,5 @@
 'use strict'
 
-import defaults from 'defaults'
 import CloudWatchClient from '../../src/cloudwatch-client'
 import LogItem from '../../src/log-item'
 
@@ -50,13 +49,13 @@ const streamsStrategies = {
 }
 
 const createClient = (options) => {
-  options = defaults(options, {
+  options = Object.assign({
     clientOptions: null,
     streamsStrategy: streamsStrategies.default,
     groupErrorCode: null,
     streamErrorCode: false,
     putRejectionCode: null
-  })
+  }, options)
   const client = new CloudWatchClient(logGroupName, logStreamName,
     options.clientOptions)
   let putPromise