Custom cross object query in custom OWL

Greetings to you all,

I am trying to configure advanced cross object search parameters in my custom BO OWL.

Here is the OWL (geoOpptID, latitude and longitude are fields of my custom BO, the other fields are loaded via association[0,1] to opportunity).

Then I've made a custom query with parameters taken from the association:

If I execute this query, it returns correct result:

Now I need to get this query to my OWL (which I've been failing to do so far)

1 . I create a query in the UI designer

2. When I try to add the query field to the search pane, I get a error.

(InnerException Message: Object reference is not set to an instance of an object.)

Any ideas how to make this work?

Thank you very much,

Michal P.