I am getting a 500: INTERNAL SERVER ERROR - This Edge Function has crashed. for my nextjs deployment on vercel.
The problem seems to be with the middleware (https://github.com/MystenLabs/walrus-sites/blob/develop/portal/server/middleware.ts) I am using.
From the deployment logs I see the following (__dirname is not defined):

ReferenceError: __dirname is not defined
    at (portal/node_modules/.pnpm/next@14.2.5_react-dom@18.3.1_react@18.3.1/node_modules/next/dist/compiled/ua-parser-js/ua-parser.js:1:17315)
    at (portal/node_modules/.pnpm/next@14.2.5_react-dom@18.3.1_react@18.3.1/node_modules/next/dist/compiled/ua-parser-js/ua-parser.js:1:17444)
    at (portal/node_modules/.pnpm/next@14.2.5_react-dom@18.3.1_react@18.3.1/node_modules/next/dist/server/web/spec-extension/user-agent.js:27:59)
    at (portal/node_modules/.pnpm/next@14.2.5_react-dom@18.3.1_react@18.3.1/node_modules/next/server.js:8:0)
    at (portal/server/middleware.js:3:29)

This would make sense if I called __dirname in my middleware, or if I imported a third party that does so, but this is not the case.

What could be the cause?