Rustls error with specific domain

I'm having a strange issue where when I try to upgrade an existing tokio::net::TcpStream to TLS I get:

IoError(Custom { kind: UnexpectedEof, error: "tls handshake eof" })

I have only observed this error with one end server. It has worked fine for numerous other ones I have tested. I am confident it is not the end server as other programs have been able to connect to it via TLS fine.

My code:

tls.connect(server_name, stream).await?

provides no unsafe features or obsolete cryptography.

Maybe the server uses rather old TLS library which only knows those obsolete, known-to-be-vulnerable-now cryptography. TLS connection can only be established if both ends agree on single cipher suite to use.

If you do need to access those vulnerable servers anyway you need other TLS libraries like the openssl which supports obsolete crypto.

I felt it might be as much. It's a shame it has such a pitiful error message.