pg_upgrade 9.5.1: pg_upgrade_support missing

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

Could not load library "$libdir/pg_upgrade_support"
FEHLER: konnte nicht auf Datei „$libdir/pg_upgrade_support“ zugreifen: No such file or directory