SQL & PL/SQL

Hi expert,
For me, it's really..really weird.
I created LOB segment (securefiles), inserted some data and check its space using DBMS_SPACE. But somehow it throws ORA-10614.
Oracle : 11.2.0.2
OS : RHEL 5

VARIABLE  UNFORMATTED_BLK         NUMBER;
VARIABLE  UNFORMATTED_BYT         NUMBER;
VARIABLE  FS1_BLK                 NUMBER;
VARIABLE  FS1_BYT                 NUMBER;
VARIABLE  FS2_BLK                 NUMBER;
VARIABLE  FS2_BYT                 NUMBER;
VARIABLE  FS3_BLK                 NUMBER;
VARIABLE  FS3_BYT                 NUMBER;
VARIABLE  FS4_BLK                 NUMBER;
VARIABLE  FS4_BYT                 NUMBER;
VARIABLE  FULL_BLK                NUMBER;
VARIABLE  FULL_BYT                NUMBER;
BEGIN
        DBMS_SPACE.SPACE_USAGE(
                SEGMENT_OWNER   => 'SF_DEMO',
                SEGMENT_NAME    => 'ASU',
                SEGMENT_TYPE    => 'LOB',
                UNFORMATTED_BLOCKS => :UNFORMATTED_BLK,
                UNFORMATTED_BYTES => :UNFORMATTED_BYT,
                FS1_BLOCKS      => :FS1_BLK,
                FS1_BYTES       => :FS1_BYT,
                FS2_BLOCKS      => :FS2_BLK,
                FS2_BYTES       => :FS2_BYT,
                FS3_BLOCKS      => :FS3_BLK,
                FS3_BYTES       => :FS3_BYT,
                FS4_BLOCKS      => :FS4_BLK,
                FS4_BYTES       => :FS4_BYT,
                FULL_BLOCKS     => :FULL_BLK,
                FULL_BYTES      => :FULL_BYT
        );
END;
/
BEGIN
*
ERROR at line 1:
ORA-10614: Operation not allowed on this segment
ORA-06512: at "SYS.DBMS_SPACE", line 190
ORA-06512: at line 2

I know that DBMS_SPACE is used only on segments in tablespaces with AUTO SEGMENT SPACE. And this is a prove that all things have been stored in ASSM tablespace.

SQL> SELECT
  2  A.SEGMENT_NAME,A.SEGMENT_TYPE,
  3  A.SEGMENT_SUBTYPE,A.TABLESPACE_NAME,B.SEGMENT_SPACE_MANAGEMENT
  4  FROM DBA_SEGMENTS A JOIN DBA_TABLESPACES B
  5  ON A.TABLESPACE_NAME=B.TABLESPACE_NAME
  6  WHERE A.OWNER='SF_DEMO';

SEGMENT_NAME              SEGMENT_TYPE       SEGMENT_SU TABLESPACE_NAME SEGMEN
------------------------- ------------------ ---------- --------------- ------
RESUME_SF                 TABLE              ASSM       SECF_TBS1       AUTO
SYS_IL0000018044C00002$$  LOBINDEX           ASSM       SECF_TBS1       AUTO
ASU                       LOBSEGMENT         SECUREFILE SECF_TBS1       AUTO

Any help appreciated.

Regards,
Yusata.