BO Condition in a derived table

Hi everyone,

When I try to create a condition in the derived table "Der_Tab_SS" (derived from Tab_SS) writing into the condition area "Der_Tab_SS"."ZFISCALWEEK" != '0' knowing that ZFISCALWEEK is a char, I get into the error message Exception, DBD, ORA-00904: "Der_Tab_SS"."ZFISCALWEEK" not valid identifier.

But the table and the fileds are correctly existing!

Which mistake am I doing? Can someone kindly help?