Using r1752 I get the error below if I call generate-sea=multipolygon,extend-sea-sectors java.lang.NullPointerException at uk.me.parabola.mkgmap.reader.osm.SeaGenerator.end(SeaGenerator.java:432) at uk.me.parabola.mkgmap.reader.osm.OsmReadingHooksChain.end(OsmReadingHooksChain.java:78) at uk.me.parabola.mkgmap.reader.osm.bin.OsmBinMapDataSource.load(OsmBinMapDataSource.java:68) at uk.me.parabola.mkgmap.main.MapMaker.loadFromFile(MapMaker.java:145) at uk.me.parabola.mkgmap.main.MapMaker.makeMap(MapMaker.java:56) at uk.me.parabola.mkgmap.main.Main$1.call(Main.java:220) at uk.me.parabola.mkgmap.main.Main$1.call(Main.java:217) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303) at java.util.concurrent.FutureTask.run(FutureTask.java:138) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:662) Using generate-sea=polygons,extend-sea-sectors works fine as usual