What does "Error: Expected at least one matching middleware" mean?

[Ethelt]

Hi, can anyone tell me what does "Error: Expected at least one matching middleware" in my Next,js middleware function mean? I couldn't find any info on it on the internet, or in Vercel and Next.js code.
It happens every time I try to access a page with English locale (en-us, en-gb, etc.), but not in other languages (pl-us works fine), unless I set the English locale as a default one. Everything works fine on my machine, but it breaks when trying to deploy it on Vercel. It happens regardless of middleware function content.

[leerob]

Could you share a link to your repository so we can take a look? Thank you!

[leerob]

Thank you! We have an open PR to fix this, should be resolved very soon.

[mismosmi]

I see the same issue. Would you let me know if this is resolved?

Thanks!

[rafael-franca]

Me too. When I added a middleware in root.

[khrome83]

I am seeing this also with the ENABLE_FILE_SYSTEM_API as well. Can you link to the PR @leerob so we can track when this is resolved?

[leerob]

Why are you using ENABLE_FILE_SYSTEM_API? Could you share more?

[Pieparker]

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