diff --git a/tslib.es6.js b/tslib.es6.js
index 15b8096..26f9f9d 100644
--- a/tslib.es6.js
+++ b/tslib.es6.js
@@ -13,11 +13,16 @@ See the Apache Version 2.0 License for specific language governing permissions
 and limitations under the License.
 ***************************************************************************** */
 /* global Reflect, Promise */
+
+var extendStatics = Object.setPrototypeOf ||
+    ({ __proto__: [] } instanceof Array && function (d, b) { d.__proto__ = b; }) ||
+    function (d, b) { for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p]; };
+
 export function __extends(d, b) {
-    for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
+    extendStatics(d, b);
     function __() { this.constructor = d; }
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
-};
+}
 
 export var __assign = Object.assign || function __assign(t) {
     for (var s, i = 1, n = arguments.length; i < n; i++) {
diff --git a/tslib.js b/tslib.js
index 72aa746..3211003 100644
--- a/tslib.js
+++ b/tslib.js
@@ -37,8 +37,12 @@ var __generator;
     }
 })
 (function (exporter) {
+    var extendStatics = Object.setPrototypeOf ||
+        ({ __proto__: [] } instanceof Array && function (d, b) { d.__proto__ = b; }) ||
+        function (d, b) { for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p]; };
+
     __extends = function (d, b) {
-        for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
+        extendStatics(d, b);
         function __() { this.constructor = d; }
         d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
     };