diff --git a/src/platform/polyfills.ts b/src/platform/polyfills.ts
index 1af3341..6bbf700 100644
--- a/src/platform/polyfills.ts
+++ b/src/platform/polyfills.ts
@@ -22,7 +22,7 @@ if (typeof Promise.withResolvers === "undefined") {
 
   // Promise.withResolvers is generic and works with subclasses - the typescript built-in decl
   // could not handle the subclassing case.
-  Promise.withResolvers = function <T>(this: AnyPromiseConstructor<T>) {
+  (Promise.prototype as any).withResolvers = function <T>(this: AnyPromiseConstructor<T>) {
     let resolve!: PromiseWithResolvers<T>["resolve"], reject!: PromiseWithResolvers<T>["reject"];
     // These variables are expected to be set after `new this()`