Upgrading Postgres 12 to 13: 'pg_upgrade.exe' fails

Question

I'm attempting to upgrade a Postgres instance from version 12 to version 13, following the steps outlined at https://www.postgresql.org/docs/13/pgupgrade.html.

From an elevated command prompt, I'm running (under Windows 10):

SET PATH=%PATH%;C:\Program Files\PostgreSQL\13\bin;

pg_upgrade.exe --old-datadir "E:\Programs\PostgreSQL\12\data" --new-datadir "E:\Programs\PostgreSQL\13\data" --old-bindir "C:\Program Files\PostgreSQL\12\bin" --new-bindir "C:\Program Files\PostgreSQL\13\bin" --old-port=5431 --new-port=5432 --jobs=5

The directories appear to be all correct, however the command returns:

Performing Consistency Checks  
-----------------------------  
Checking cluster versions                                   ok  
  
*failure*  
Consult the last few lines of "pg_upgrade_server_start.log" or "pg_upgrade_server.log" for  
the probable cause of the failure.  
  
connection to database failed: could not connect to server: Connection refused (0x0000274D/10061)  
        Is the server running on host "localhost" (::1) and accepting  
        TCP/IP connections on port 5431?  
could not connect to server: Connection refused (0x0000274D/10061)  
        Is the server running on host "localhost" (127.0.0.1) and accepting  
        TCP/IP connections on port 5431?  
  
could not connect to source postmaster started with the command:  
"C:/Program Files/PostgreSQL/12/bin/pg_ctl" -w -l "pg_upgrade_server.log" -D "E:/Programs/PostgreSQL/12/data" -o "-p 5431 -b " start  
Failure, exiting  

pg_upgrade_server_start.log says:

command: "C:/Program Files/PostgreSQL/12/bin/pg_ctl" -w -l "pg_upgrade_server.log" -D "E:/Programs/PostgreSQL/12/data" -o "-p 5431 -b " start >> "pg_upgrade_server_start.log" 2>&1
The program "postgres" was found by "C:/Program Files/PostgreSQL/12/bin/pg_ctl"
but was not the same version as pg_ctl.
Check your installation.

I'm at a loss; what might be wrong, and how can I successfully perform this procedure?

Answer 1

The answer had to do with the option "Beta: Use Unicode UTF-8 for worldwide language support" being checked in my locale settings in Windows.

I disabled that option and restarted the computer, the upgrade went without issues after that.