So siehts ganz gut aus !

node_modules/core-js/modules/es7.object.define-setter.js

@@ -0,0 +1,12 @@
+'use strict';
+var $export = require('./_export');
+var toObject = require('./_to-object');
+var aFunction = require('./_a-function');
+var $defineProperty = require('./_object-dp');
+
+// B.2.2.3 Object.prototype.__defineSetter__(P, setter)
+require('./_descriptors') && $export($export.P + require('./_object-forced-pam'), 'Object', {
+  __defineSetter__: function __defineSetter__(P, setter) {
+    $defineProperty.f(toObject(this), P, { set: aFunction(setter), enumerable: true, configurable: true });
+  }
+});