Hi Michał I believe that I have now found the problem thanks to your example. If I'm right, then the problem occurs when there are some cities that do not have a country assigned and also that the total number of cities is greater than 64k and the number of cities with a country is less than that. So it is mostly just unlucky based on the amount of data. With a perfect bounds file, then every city should have a country and the problem would not happen I think, so there was probably some significance about the tiles being at the edge in a different country. If not using a bounds file, then the problem is much more likely to happen and may explain why I often see problems with maps without bounds files. The fix is on the sort2 branch at r3163 or greater: http://www.mkgmap.org.uk/download/mkgmap-sort2-r3163.zip ..Steve