isConstructorOrProto adapted from PR

index.js

@@ -70,7 +70,7 @@ module.exports = function (args, opts) {
  var o = obj;
  for (var i = 0; i < keys.length-1; i++) {
  var key = keys[i];
- if (key === '__proto__') return;
+ if (isConstructorOrProto(o, key)) return;
  if (o[key] === undefined) o[key] = {};
  if (o[key] === Object.prototype || o[key] === Number.prototype
  || o[key] === String.prototype) o[key] = {};
@@ -79,7 +79,7 @@ module.exports = function (args, opts) {
  }
 
  var key = keys[keys.length - 1];
- if (key === '__proto__') return;
+ if (isConstructorOrProto(o, key)) return;
  if (o === Object.prototype || o === Number.prototype
  || o === String.prototype) o = {};
  if (o === Array.prototype) o = [];
@@ -243,3 +243,7 @@ function isNumber (x) {
  return /^[-+]?(?:\d+(?:\.\d*)?|\.\d+)(e[-+]?\d+)?$/.test(x);
 }
 
+
+function isConstructorOrProto (obj, key) {
+ return key === 'constructor' && typeof obj[key] === 'function' || key === '__proto__';
+}