/404 wont render when using expressjs with astro/node as middleware

[bathtubfulloftoast]

Astro Info

Astro                    v5.16.4
Vite                     v6.4.1
Node                     v25.1.0
System                   Linux (x64)
Package Manager          pnpm
Output                   static
Adapter                  @astrojs/node (v9.5.1)
Integrations             none

If this issue only occurs in one browser, which browser is a problem?

No response

Describe the Bug

when 404.astro is provided

going to /404 in the browser will lead to a 500 with the following error printed in the console

13:32:53 [ERROR] TypeError: mod.page is not a function
    at NodeApp.render (file:///home/nova/Downloads/absent-axis/dist/server/chunks/_@astrojs-ssr-adapter_DNZPGUso.mjs:4695:55)
    at async file:///home/nova/Downloads/absent-axis/dist/server/chunks/_@astrojs-ssr-adapter_DNZPGUso.mjs:5173:24
    at async file:///home/nova/Downloads/absent-axis/dist/server/chunks/_@astrojs-ssr-adapter_DNZPGUso.mjs:5206:7

this only happens when running server.mjs (note this is the server.mjs provided in the docs for astro/node)

What's the expected result?

allowing the middleware to handle the 404

Link to Minimal Reproducible Example

https://stackblitz.com/edit/github-xdbdlg1n?file=server.js

Participation

• I am willing to submit a pull request for this issue.

[bathtubfulloftoast]

please forgive me if the stackblitz page is terrible ive never used stackblitz

[rburgst]

same is true for fastify