Q: Modify Index Subpartition NOPARALLEL ? (Drawing a blank)

I have a need to rebuild a bunch of indexes (partition and subpartitions) into a new tablespace.

I have the rebuild working fine for subpartitions like so:

alter index CTAYLOR.MY_INDEX01 rebuild subpartition SYS_SUBP42599 tablespace USERS online parallel 8;

What I cannot figure out is how to modify the subpartition back to NOPARALLEL. I've tried:
alter index CTAYLOR.MY_INDEX01 modify subpartition SYS_SUBP42599 NOPARALLEL; alter index CTAYLOR.MY_INDEX01 subpartition SYS_SUBP42599 NOPARALLEL;

I know I can issue another rebuild stmt NOPARALLEL but that seems crazy. There has to be a simple way to modify the subpartition back to noparallel and I can't figure out from manuals how to get to it (sheepish).

Any help?