diff --git a/src/index.js b/src/index.js
index 5e34095..3752b69 100644
--- a/src/index.js
+++ b/src/index.js
@@ -22,7 +22,7 @@ const buildHelper = template(`
             },
         });
         if (Object.setPrototypeOf){
-            Object.setPrototypeOf(ExtendableBuiltin, cls);
+            Object.setPrototypeOf(ExtendableBuiltin, cls, this.constructor);
         } else {
             ExtendableBuiltin.__proto__ = cls;
         }