Issue with Unicode

[errand]

I get empty responce when trying to fetch with Cyrillic params.
Example
localhost:8000/api/buildings?filter[building_class]=Komfort will response ok

And
localhost:8000/api/buildings?filter[building_class]=Комфорт will return empty response.

When I use common Laravel query builder where is no such issue.

return Building::where('building_class', 'Комфорт')->get();

I suppose the problem is in JSON format storing the Unicode.

I wonder how to construct GET request for filter in proper format?