diff --git a/deno.json b/deno.json
index aafaa17..c01d8d3 100644
--- a/deno.json
+++ b/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@oak/acorn",
-  "version": "0.5.0",
+  "version": "0.5.1-alpha.1",
   "exports": {
     ".": "./mod.ts",
     "./context": "./context.ts",
diff --git a/http_server_bun.ts b/http_server_bun.ts
index c7a23e3..a9ee229 100644
--- a/http_server_bun.ts
+++ b/http_server_bun.ts
@@ -17,6 +17,10 @@ import type {
 } from "./types_internal.ts";
 import { createPromiseWithResolvers } from "./util.ts";
 
+if (!("URLPattern" in globalThis)) {
+  await import("npm:urlpattern-polyfill");
+}
+
 type TypedArray =
   | Uint8Array
   | Uint16Array