ORA-31608: specified object of type OBJECT_GRANT not found

SQL> SELECT DBMS_METADATA.GET_GRANTED_DDL('OBJECT_GRANT','DILIP') from dual;
ERROR:
ORA-31608: specified object of type OBJECT_GRANT not found
ORA-06512: at "SYS.DBMS_SYS_ERROR", line 86
ORA-06512: at "SYS.DBMS_METADATA", line 3915
ORA-06512: at "SYS.DBMS_METADATA", line 5826
ORA-06512: at line 1


no rows selected
SQL>
SQL>
SQL>
SQL> grant select on dual to dilip;
Grant succeeded.
SQL> SELECT DBMS_METADATA.GET_GRANTED_DDL('OBJECT_GRANT','DILIP') from dual;
DBMS_METADATA.GET_GRANTED_DDL('OBJECT_GRANT','DILIP')
--------------------------------------------------------------------------------
  GRANT SELECT ON "SYS"."DUAL" TO "DILIP";