pg_basebackup fails on inactive slave

I have PostgreSQL 9.2.6 (pgdg-92-centos.repo) on CentOS 6.4 amd64.

I have a problem when I do pg_basebackup on slave with following options
pg_basebackup -w -U replication -h 127.0.0.1 -p 5432\
-D /mnt/basebackups_last/ -F p -l "backup_24.02.2015" -x
I got message:
pg_basebackup: could not get transaction log end position from server:
FATAL: could not find any WAL files

-x - will by default take WALs on end of basebackup.

Is it normal because database master/slave aren't all that active at a time
of taking this
basebackup that basebackup on slave fail with this message?
Should I remove "-x" option, it's not strictly needed because I have a
service that is fetching
wals that can be combined with basebackups?

Thanks
--
Stanislav Antic