diff --git a/package-lock.json b/package-lock.json
index 4e4b98b..1a8fdac 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -11,7 +11,7 @@
       "devDependencies": {
         "@types/node": "^8.10.54",
         "is-mergeable-object": "1.1.0",
-        "is-plain-object": "^2.0.4",
+        "is-plain-object": "^5.0.0",
         "jsmd": "^1.0.2",
         "rollup": "^1.23.1",
         "rollup-plugin-commonjs": "^10.1.0",
@@ -359,21 +359,9 @@
       "dev": true
     },
     "node_modules/is-plain-object": {
-      "version": "2.0.4",
-      "resolved": "https://registry.npmjs.org/is-plain-object/-/is-plain-object-2.0.4.tgz",
-      "integrity": "sha512-h5PpgXkWitc38BBMYawTYMWJHFZJVnBquFE57xFpjB8pJFiF6gZ+bU+WyI/yqXiFR5mdLsgYNaPe8uao6Uv9Og==",
-      "dev": true,
-      "dependencies": {
-        "isobject": "^3.0.1"
-      },
-      "engines": {
-        "node": ">=0.10.0"
-      }
-    },
-    "node_modules/is-plain-object/node_modules/isobject": {
-      "version": "3.0.1",
-      "resolved": "https://registry.npmjs.org/isobject/-/isobject-3.0.1.tgz",
-      "integrity": "sha1-TkMekrEalzFjaqH5yNHMvP2reN8=",
+      "version": "5.0.0",
+      "resolved": "https://registry.npmjs.org/is-plain-object/-/is-plain-object-5.0.0.tgz",
+      "integrity": "sha512-VRSzKkbMm5jMDoKLbltAkFQ5Qr7VDiTFGXxYFXXowVj387GeGNOCsOH6Msy00SGZ3Fp84b1Naa1psqgcCIEP5Q==",
       "dev": true,
       "engines": {
         "node": ">=0.10.0"
@@ -1135,21 +1123,10 @@
       "dev": true
     },
     "is-plain-object": {
-      "version": "2.0.4",
-      "resolved": "https://registry.npmjs.org/is-plain-object/-/is-plain-object-2.0.4.tgz",
-      "integrity": "sha512-h5PpgXkWitc38BBMYawTYMWJHFZJVnBquFE57xFpjB8pJFiF6gZ+bU+WyI/yqXiFR5mdLsgYNaPe8uao6Uv9Og==",
-      "dev": true,
-      "requires": {
-        "isobject": "^3.0.1"
-      },
-      "dependencies": {
-        "isobject": {
-          "version": "3.0.1",
-          "resolved": "https://registry.npmjs.org/isobject/-/isobject-3.0.1.tgz",
-          "integrity": "sha1-TkMekrEalzFjaqH5yNHMvP2reN8=",
-          "dev": true
-        }
-      }
+      "version": "5.0.0",
+      "resolved": "https://registry.npmjs.org/is-plain-object/-/is-plain-object-5.0.0.tgz",
+      "integrity": "sha512-VRSzKkbMm5jMDoKLbltAkFQ5Qr7VDiTFGXxYFXXowVj387GeGNOCsOH6Msy00SGZ3Fp84b1Naa1psqgcCIEP5Q==",
+      "dev": true
     },
     "is-reference": {
       "version": "1.1.4",
diff --git a/package.json b/package.json
index 3b8507b..b1283d5 100644
--- a/package.json
+++ b/package.json
@@ -28,7 +28,7 @@
   "devDependencies": {
     "@types/node": "^8.10.54",
     "is-mergeable-object": "1.1.0",
-    "is-plain-object": "^2.0.4",
+    "is-plain-object": "^5.0.0",
     "jsmd": "^1.0.2",
     "rollup": "^1.23.1",
     "rollup-plugin-commonjs": "^10.1.0",
@@ -38,6 +38,5 @@
     "typescript": "=2.2.2",
     "uglify-js": "^3.6.1"
   },
-  "license": "MIT",
-  "dependencies": {}
+  "license": "MIT"
 }
diff --git a/test/custom-is-mergeable-object.js b/test/custom-is-mergeable-object.js
index ea247ab..f58bbb8 100644
--- a/test/custom-is-mergeable-object.js
+++ b/test/custom-is-mergeable-object.js
@@ -1,36 +1,72 @@
-var merge = require('../')
-var test = require('tape')
+const merge = require(`..`)
+const test = require(`tape`)
 
-test('isMergeableObject function copying object over object', function(t) {
-	var src = { key: { isMergeable: false }, baz: 'yes' }
-	var target = { key: { foo: 'wat' }, baz: 'whatever' }
+test(`isMergeableObject function copying object over object`, t => {
+	const src = { key: { isMergeable: false }, baz: `yes` }
+	const target = { key: { foo: `wat` }, baz: `whatever` }
 
 	function isMergeableObject(object) {
-		return object && typeof value === 'object' && object.isMergeable !== false
+		return object && typeof value === `object` && object.isMergeable !== false
 	}
 
-	var res = merge(target, src, {
-		isMergeableObject: isMergeableObject
+	const res = merge(target, src, {
+		isMergeableObject,
 	})
 
-	t.deepEqual(res, { key: { isMergeable: false }, baz: 'yes' })
-	t.equal(res.key, src.key, 'Object has the same identity and was not cloned')
+	t.deepEqual(res, { key: { isMergeable: false }, baz: `yes` })
+	t.equal(res.key, src.key, `Object has the same identity and was not cloned`)
 	t.end()
 })
 
-test('isMergeableObject function copying object over nothing', function(t) {
-	var src = { key: { isMergeable: false, foo: 'bar' }, baz: 'yes' }
-	var target = { baz: 'whatever' }
+test(`isMergeableObject function copying object over nothing`, t => {
+	const src = { key: { isMergeable: false, foo: `bar` }, baz: `yes` }
+	const target = { baz: `whatever` }
 
 	function isMergeableObject(object) {
-		return object && typeof value === 'object' && object.isMergeable !== false
+		return object && typeof value === `object` && object.isMergeable !== false
 	}
 
-	var res = merge(target, src, {
-		isMergeableObject: isMergeableObject
+	const res = merge(target, src, {
+		isMergeableObject,
 	})
 
-	t.deepEqual(res, { key: { isMergeable: false, foo: 'bar' }, baz: 'yes' })
-	t.equal(res.key, src.key, 'Object has the same identity and was not cloned')
+	t.deepEqual(res, { key: { isMergeable: false, foo: `bar` }, baz: `yes` })
+	t.equal(res.key, src.key, `Object has the same identity and was not cloned`)
+	t.end()
+})
+
+test(`example from readme`, t => {
+	const { isPlainObject } = require(`is-plain-object`)
+
+	function SuperSpecial() {
+		this.special = `oh yeah man totally`
+	}
+
+	const instantiatedSpecialObject = new SuperSpecial()
+
+	const target = {
+		someProperty: {
+			cool: `oh for sure`,
+		},
+	}
+
+	const source = {
+		someProperty: instantiatedSpecialObject,
+	}
+
+	const defaultOutput = merge(target, source)
+
+	t.equal(defaultOutput.someProperty.cool, `oh for sure`)
+	t.equal(defaultOutput.someProperty.special, `oh yeah man totally`)
+	t.equal(defaultOutput.someProperty instanceof SuperSpecial, false)
+
+	const customMergeOutput = merge(target, source, {
+		isMergeableObject: isPlainObject,
+	})
+
+	t.equal(customMergeOutput.someProperty.cool, undefined)
+	t.equal(customMergeOutput.someProperty.special, `oh yeah man totally`)
+	t.equal(customMergeOutput.someProperty instanceof SuperSpecial, true)
+
 	t.end()
 })