client_encoding is WIN1252 on ErrorMessage at the StartupMessage

I’m developing the wire protocol on programmable logic controller (PLC) to communicate with the backend server.

The PostgreSQL server run on Windows 10 French Canadian.

The client_encoding on the server and database encoding is UTF8.

The collation and character type are French_Canada.1252.

The PLC is UTF8.

After TCP/IP connection, the PLC send the “StartupMessage” but receive an “ErrorResponse” because no access right.

The error message is in WIN1252 not UTF8!

If grant connect access to user and get data from database all is UTF8!

Is it a bug or bad setup?

Regards,