pg_upgrade 9.5.1: pg_upgrade_support missing

Hello,

i tried to migrate a database cluster from pg 9.4.1 to 9.5.1 with
pg_upgrade. I got the follwing error:

c:\Temp>"C:\Program Files\PostgreSQL\9.5\bin\pg_upgrade" -b "C:\Program
> Files\PostgreSQL\9.4\bin" -B "C:\Program Files\PostgreSQL\9.5\bin" -
> d "C:\Program Files\PostgreSQL\9.4\data" -D "C:\Program
> Files\PostgreSQL\9.5\data" -p 5433 -P 5432 -U postgres
> Performing Consistency Checks
> -----------------------------
> Checking cluster versions ok
> Checking database user is the install user ok
> Checking database connection settings ok
> Checking for prepared transactions ok
> Checking for reg* system OID user data types ok
> Checking for contrib/isn with bigint-passing mismatch ok
> Creating dump of global objects ok
> Creating dump of database schemas
> ok
> Checking for presence of required libraries fatal
> Your installation references loadable libraries that are missing from the
> new installation. You can add these libraries to the new installation,
> or remove the functions using them from the old installation. A list of
> problem libraries is in the file:
> loadable_libraries.txt
> Failure, exiting

The file loadable_libraries.txt contains:
>
>
> Could not load library "$libdir/pg_upgrade_support"
> FEHLER: konnte nicht auf Datei „$libdir/pg_upgrade_support“ zugreifen: No
> such file or directory

I tried to copy the dll from the 9.4 version but the interface seems not to
be compatible.

I use postgres under Windows 7 64 Bit.

Note: This is a question first asked here:
https://www.pg-forum.de/viewtopic.php?f=54&t=7495

Thanks,
Tobias