diff --git a/.changeset/ten-flowers-begin.md b/.changeset/ten-flowers-begin.md
new file mode 100644
index 00000000..b5553413
--- /dev/null
+++ b/.changeset/ten-flowers-begin.md
@@ -0,0 +1,5 @@
+---
+"@opennextjs/cloudflare": patch
+---
+
+define \_\_filename globally
diff --git a/packages/cloudflare/src/cli/build/bundle-server.ts b/packages/cloudflare/src/cli/build/bundle-server.ts
index 06282d53..b2c6b366 100644
--- a/packages/cloudflare/src/cli/build/bundle-server.ts
+++ b/packages/cloudflare/src/cli/build/bundle-server.ts
@@ -136,10 +136,11 @@ export async function bundleServer(buildOpts: BuildOptions): Promise<void> {
     platform: "node",
     banner: {
       js: `
-// __dirname is used by unbundled js files (which don't inherit the __dirname present in the define field)
+// Used by unbundled js files (which don't inherit the __dirname present in the define field)
 // so we also need to set it on the global scope
 // Note: this was hit in the next/dist/compiled/@opentelemetry/api module
 globalThis.__dirname ??= "";
+globalThis.__filename ??= "";
 
 // Do not crash on cache not supported
 // https://github.com/cloudflare/workerd/pull/2434