BAPI_FIXEDASSET_CHANGE problem with changing WBS element

Hello,

I have a problem with changing WBS element in account assignment data. I'm filling out correct structure of bapi with correct data, but on the return I'm getting message "No changes made". I know that it's not a problem with the conversion routine. I'm also changing WBS element on time dependent tab and that is working fine. If you have any ideas please help me.

Sample of my code:

data: ps_invest TYPE bapi1022_feglg010,

ps_investx TYPE bapi1022_feglg010x.

ps_invest-wbs_elem = ps_mass_upd-posnr.

ps_investx-wbs_element = 'X'.