Hi, Finally I found the cause of the problem. I found deeper inside my calls, a function which has to return an integer column from a RECORD rec variable. The rec is assigned with the following statement: EXECUTE 'SELECT pk AS "PK" FROM "my_table" WHERE my_where_clause' INTO rec. When my_where_clause is not fulfilled, rec is initialized somehow with null. The exception is rised at the end where I call: RETURN rec."PK" Maybe someone can explain this behavior. TIA, Sabin