Cannot trigger descending sort by click the header

[addy_hu]

I have a listGridField: accountId, its displayField is accountName and it has no optionDataSource set. I cannot trigger the descending sort by click the header of the field : when I first click the header, a sort by asc is correctly triggered; then I reclick the header, nothing happens, the expected descending sort is not triggered.
However the sort by desc can always be triggered after I click the menuItem "Sort Descending".
Any help would be appreciated.

Using:
SmartGwt 2.4