diff --git a/src/index.js b/src/index.js
index cffa2b7..63c6adc 100644
--- a/src/index.js
+++ b/src/index.js
@@ -20,9 +20,7 @@ export function nestie(input, glue) {
 				output = output || tmp;
 			}
 
-			if (key == '__proto__') {
-				break;
-			}
+			if (key == '__proto__' || key == 'constructor' || key == 'prototype') break;
 
 			if (i < arr.length) {
 				if (key in tmp) {
diff --git a/test/index.js b/test/index.js
index 9b361ee..dca86c4 100644
--- a/test/index.js
+++ b/test/index.js
@@ -428,7 +428,7 @@ test('array :: kitchen', () => {
 	]);
 });
 
-test('proto pollution :: toplevel', () => {
+test('proto pollution :: __proto__ :: toplevel', () => {
 	let output = nestie({
 		'__proto__.foobar': 123
 	});
@@ -438,7 +438,7 @@ test('proto pollution :: toplevel', () => {
 	assert.is(tmp.foobar, undefined);
 });
 
-test('proto pollution :: midlevel', () => {
+test('proto pollution :: __proto__ :: midlevel', () => {
 	let output = nestie({
 		'aaa.__proto__.foobar': 123
 	});
@@ -448,7 +448,7 @@ test('proto pollution :: midlevel', () => {
 	assert.is(tmp.foobar, undefined);
 });
 
-test('proto pollution :: sibling', () => {
+test('proto pollution :: __proto__ :: sibling', () => {
 	let output = nestie({
 		'aaa.bbb': 'abc',
 		'__proto__.foobar': 123,
@@ -470,4 +470,70 @@ test('proto pollution :: sibling', () => {
 	assert.is(tmp.foobar, undefined);
 });
 
+test('proto pollution :: prototype', () => {
+	let output = nestie({
+		'a.prototype.hello': 'world',
+	});
+
+	assert.equal(output, {
+		a: {
+			// converted, then aborted
+		}
+	});
+
+	assert.is.not({}.hello, 'world');
+	assert.is({}.hello, undefined);
+});
+
+test('proto pollution :: constructor :: direct', () => {
+	function Custom() {
+		//
+	}
+
+	let output = nestie({
+		'a.constructor': Custom,
+		'foo.bar': 123,
+	});
+
+	assert.equal(output, {
+		a: {
+			// stopped
+		},
+		foo: {
+			bar: 123,
+		}
+	});
+
+	// Check existing object
+	assert.is.not(output.a.constructor, Custom);
+	assert.not.instance(output.a, Custom);
+	assert.instance(output.a.constructor, Object, '~> 123 -> {}');
+	assert.is(output.a.hasOwnProperty('constructor'), false);
+
+	let tmp = {}; // Check new object
+	assert.is.not(tmp.constructor, Custom);
+	assert.not.instance(tmp, Custom);
+
+	assert.instance(tmp.constructor, Object, '~> 123 -> {}');
+	assert.is(tmp.hasOwnProperty('constructor'), false);
+});
+
+test('proto pollution :: constructor :: nested', () => {
+	let output = nestie({
+		'constructor.prototype.hello': 'world',
+		'foo': 123,
+	});
+
+	assert.equal(output, {
+		foo: 123
+	});
+
+	assert.is(output.hasOwnProperty('constructor'), false);
+	assert.is(output.hasOwnProperty('hello'), false);
+
+	let tmp = {};
+	assert.is(tmp.hasOwnProperty('constructor'), false);
+	assert.is(tmp.hasOwnProperty('hello'), false);
+});
+
 test.run();