[mkgmap-dev] coastline boundaries

Hi, How can I filter out all lines wich are part of boundaries that have a natural=coastline tag? For instance this way: http://www.openstreetmap.org/way/39862450 On my map I dont want to see the boundary lines along the coastlines, but in the style files I can't filter boundary=administrative & natural!=coastline. Somehow administrative boundaries are processed without the coastline tags. Or can I use osmfilter to delete all ways that are tagged with natural=coastline AND are part of a boundary relation?