Replicating redis foreign table via postgresql synchronous replication

I have synchronous replication between db server, DB1 and DB2. Tested, working.
I have a redis server (RD1), integrated with DB1 (master) via redis_fdw, no issues here. I was expecting foreign redis table to by synched between DB1 and DB2 after sync replication but it does not. I can see the table on DB2 (slave) when I type “d” in slave psql but when I want to select records, I get: “ERROR: could not access file “$libdir/redis_fdw”: No such file or directory”. The question is, how can I get redis updates from postgresql slave via postgresql sync. It is possible? I can integrate the slave DB with redis server but that would break the DB sync.
Thanks.