ORA-39921: Default Partition (Table) Tablespace USERS for TP not contained in transportable set

When doing transportable tablespace, I get the following errors when run the TTS set check procedure:

SQL> EXECUTE dbms_tts.transport_set_check('TS_D1,TS_D2,TS_D3,TS_D4',TRUE); 

PL/SQL procedure successfully completed.

SQL> select * from sys.transport_set_violations;

VIOLATIONS

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ORA-39921: Default Partition (Table) Tablespace USERS for TP not contained in transportable set.

    The problem is that the default tablespace of the partition table is not in the tablespace we need transported, we should change it:

ALTER TABLE ... MODIFY DEFAULT
ATTRIBUTES TABLESPACE ...; 

ALTER TABLE TP MODIFY DEFAULT ATTRIBUTES TABLESPACE ts_d1;

After I change it, I run the TTS set check procedure again,it's OK:

SQL> EXECUTE dbms_tts.transport_set_check('TS_D1,TS_D2,TS_D3,TS_D4',TRUE); 

PL/SQL procedure successfully completed.

SQL> select * from sys.transport_set_violations;

no rows selected