diff --git a/bench.js b/bench.js
index 18506e8..849b809 100644
--- a/bench.js
+++ b/bench.js
@@ -1,6 +1,6 @@
 'use strict';
 /* globals bench */
-const m = require('./');
+const m = require('.');
 
 bench('get', () => {
 	const f1 = {foo: {bar: 1}};
diff --git a/index.js b/index.js
index 15282bb..189831c 100644
--- a/index.js
+++ b/index.js
@@ -1,6 +1,14 @@
 'use strict';
 const isObj = require('is-obj');
 
+const disallowedKeys = [
+	'__proto__',
+	'prototype',
+	'constructor'
+];
+
+const isValidPath = pathSegments => !pathSegments.some(segment => disallowedKeys.includes(segment));
+
 function getPathSegments(path) {
 	const pathArr = path.split('.');
 	const parts = [];
@@ -16,6 +24,10 @@ function getPathSegments(path) {
 		parts.push(p);
 	}
 
+	if (!isValidPath(parts)) {
+		return [];
+	}
+
 	return parts;
 }
 
@@ -26,6 +38,9 @@ module.exports = {
 		}
 
 		const pathArr = getPathSegments(path);
+		if (pathArr.length === 0) {
+			return;
+		}
 
 		for (let i = 0; i < pathArr.length; i++) {
 			if (!Object.prototype.propertyIsEnumerable.call(obj, pathArr[i])) {
@@ -58,6 +73,9 @@ module.exports = {
 
 		const root = obj;
 		const pathArr = getPathSegments(path);
+		if (pathArr.length === 0) {
+			return;
+		}
 
 		for (let i = 0; i < pathArr.length; i++) {
 			const p = pathArr[i];
diff --git a/package.json b/package.json
index 384734a..c9b0f58 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "dot-prop",
-  "version": "4.2.0",
+  "version": "4.2.1",
   "description": "Get, set, or delete a property from a nested object using a dot path",
   "license": "MIT",
   "repository": "sindresorhus/dot-prop",
@@ -38,9 +38,9 @@
     "is-obj": "^1.0.0"
   },
   "devDependencies": {
-    "ava": "*",
+    "ava": "1.4.1",
     "matcha": "^0.7.0",
-    "xo": "*"
+    "xo": "0.24.0"
   },
   "xo": {
     "esnext": true
diff --git a/readme.md b/readme.md
index fab3b7a..0e18f78 100644
--- a/readme.md
+++ b/readme.md
@@ -85,6 +85,8 @@ Path of the property in the object, using `.` to separate each nested key.
 
 Use `\\.` if you have a `.` in the key.
 
+The following path components are invalid and results in `undefined` being returned: `__proto__`, `prototype`, `constructor`.
+
 #### value
 
 Type: `any`
diff --git a/test.js b/test.js
index 5fb3735..dbbc182 100644
--- a/test.js
+++ b/test.js
@@ -1,5 +1,5 @@
 import test from 'ava';
-import m from './';
+import m from '.';
 
 test('get', t => {
 	const f1 = {foo: {bar: 1}};
@@ -199,3 +199,10 @@ test('has', t => {
 	t.is(m.has({'foo.baz': {bar: true}}, 'foo\\.baz.bar'), true);
 	t.is(m.has({'fo.ob.az': {bar: true}}, 'fo\\.ob\\.az.bar'), true);
 });
+
+test('prevent setting/getting `__proto__`', t => {
+	m.set({}, '__proto__.unicorn', '🦄');
+	t.not({}.unicorn, '🦄'); // eslint-disable-line no-use-extend-native/no-use-extend-native
+
+	t.is(m.get({}, '__proto__'), undefined);
+});