I noticed the following by reviewing the cvs commit messages: The MapArchObject.region field is not explicitly initialized in the constructor. Therefore it will be initialized with null. But the method writeMapArch has the following code in it: | if (region.length() > 0) | stream.write("region "+region+"\n"); That could probably cause a NullPointerException when saving the map, thus leaving behind a incompletely written file. Therefore, the proposed patch seem good to me. But I'd rather write | private String region = ""; // the region the instead of | private String region = new String(); // the region the