diff --git a/src/presets/cloudflare.ts b/src/presets/cloudflare.ts
index d0064a05..a2052f34 100644
--- a/src/presets/cloudflare.ts
+++ b/src/presets/cloudflare.ts
@@ -35,7 +35,7 @@ const cloudflarePreset: Preset = {
     ),
   },
   inject: {},
-  polyfill: [],
+  polyfill: ["unenv/runtime/polyfill/cloudflare"],
   external: cloudflareNodeCompatModules.map((p) => `node:${p}`),
 };
 
diff --git a/src/runtime/polyfill/cloudflare.ts b/src/runtime/polyfill/cloudflare.ts
new file mode 100644
index 00000000..ecd83240
--- /dev/null
+++ b/src/runtime/polyfill/cloudflare.ts
@@ -0,0 +1 @@
+(globalThis as any).__env__ = {};