diff --git a/lib/util.js b/lib/util.js
index 0d613ed5..92235049 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -9,7 +9,9 @@ exports.hasKeys = function(object) {
 };
 
 var hasOwn;
-exports.hasOwn = hasOwn = Object.hasOwn || Object.prototype.hasOwnProperty.call;
+exports.hasOwn = hasOwn = Object.hasOwn || function(obj, prop) {
+  return Object.prototype.hasOwnProperty.call(obj, prop);
+};
 
 // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isInteger#Polyfill
 exports.isInteger = Number.isInteger || function(value) {