Missing polygon data in reverse geocode results

I'm trying to execte the following reverse geocode request:

http://open.mapquestapi.com/nominatim/v1/reverse.php?format=json&key=<my...

I'm getting correct response, but geojson attribute is missing.

If I do the same request to nominatim.openstreetmap.org geojson attribute is present:

http://nominatim.openstreetmap.org/reverse?format=json&polygon_geojson=1...