creating a new object (measure) with IIF function on BW Olap universe and getting a mdx error

hello

i have a universe based on a BEX query

i want to create a new object (a measure) with the IIF(,,) function

i created the following select:

<EXPRESSION>

IIF ([0STKEYFIG].currentmember.properties("[20STKEYFIG]") = "0304",1,0)

</EXPRESSION>

And I get an mdx error when trying to use it in a webi. This is an old UNV. Any help would be appreciated.

Error:

Database error: Error in MDDataSetBW.GetCellData. Invalid MDX command with <usrdf_property>.VALUE. (IES 10901) (WIS 10901)