Can't change tcp_keepalives_idle

Hi,

Change tcp_keepalives_idle in postgresql.conf from 0 to 300 , then pg_ctl reload but it stays with the old 0 value.
Tried restart and it did not work. PG Log says it was changed.
Reset_cal marked OK, but no real change ( ins how)

-[ RECORD 1 ]---+-----------------------------------------------------
name | tcp_keepalives_idle
setting | 0
unit | s
category | Connections and Authentication / Connection Settings
short_desc | Time between issuing TCP keepalives.
extra_desc | A value of 0 uses the system default.
context | user
vartype | integer
source | session
min_val | 0
max_val | 2147483647
enumvals |
boot_val | 0
reset_val | 1800
sourcefile |
sourceline |
pending_restart | f

Thanks

Danny