I've added --embedflashassets option to khamake and now flash target gives me this compilation error:

.../Kha/Backends/Flash/kha/LoaderImpl.hx:105: characters 16-95 : haxe.io.Bytes should be haxe.io.BytesData
.../Kha/Backends/Flash/kha/LoaderImpl.hx:105: characters 16-95 : haxe.io.Bytes should be flash.utils.ByteArray
.../Kha/Backends/Flash/kha/LoaderImpl.hx:105: characters 16-95 : For function argument 'bytes'

Bitrod, not used in a while, will take care of it...