Increase index storage need index rebuild?

One of my index is reaching it max extents.  Somehow in my memory that I need to rebuild the index after modify the storage?

I did it on the test server first just to see whether I do need the rebuild.

alter index index_name storage (next 6M);

alter index index_name storage (maxextents 3500);

Then after the modification I checked the status of index and it still seem to be valid.

So I guess the modification of storage doesn't require index rebuild after all?