Grid: calling setSortOrder with the current sort order resets the sort orde

I have a sorting problem with Grid in Vaadin 7.5.6:

I need to remember my sort order while refeshing the data in my container, so i can set it again later.

for this, i use something like the following code

sort("SEVERITY", SortDirection.DESCENDING)); List<SortOrder> so1 = getSortOrder(); refreshData(); setSortOrder(so1); But when I call setSortOrder, the variable so1 is reset to an empty list, and the sort order in the table is lost, resulting in an unsorted table.
This also happens if I remove the call to refreshData.

Any Ideas what is happening here?