hot standby questions

Hi

Just trying to put together the hot_standby setup
All docs I read are pointing to use as prefered method to use pg_basebackup to set the base
So far so good
But

psql postgres -c "select pg_start_backup('backup')"
pg_basebackup -D /var/lib/pgsql/sample -Ft -z -P
psql postgres -c "select pg_stop_backup()"

will get me on target
< 2017-08-02 22:09:45.348 CDT >LOG: database system was interrupted; last known up at 2017-08-02 22:06:28 CDT
< 2017-08-02 22:09:45.353 CDT >LOG: entering standby mode
< 2017-08-02 22:09:45.353 CDT >LOG: invalid primary checkpoint record
< 2017-08-02 22:09:45.353 CDT >LOG: invalid secondary checkpoint record
< 2017-08-02 22:09:45.353 CDT >PANIC: could not locate a valid checkpoint record
< 2017-08-02 22:09:45.523 CDT >LOG: startup process (PID 10895) was terminated by signal 6: Aborted
< 2017-08-02 22:09:45.523 CDT >LOG: aborting startup due to startup process failure

where as
psql postgres -c "select pg_start_backup('backup')"
pg_basebackup -D /var/lib/pgsql/sample -Ft -z -P -x
psql postgres -c "select pg_stop_backup()"

I am good to go

Pretty much every where I looked at -x is not mentioned to be used

So what gives ? What did I miss ? It's gotta be soomething

Thanks
Armand