Index: trunk/src/org/openstreetmap/josm/io/GeoJSONWriter.java
===================================================================
--- trunk/src/org/openstreetmap/josm/io/GeoJSONWriter.java	(revision 12435)
+++ trunk/src/org/openstreetmap/josm/io/GeoJSONWriter.java	(revision 12439)
@@ -107,5 +107,5 @@
             if (w != null) {
                 final JsonArrayBuilder array = getCoorsArray(w.getNodes());
-                if (ElemStyles.hasAreaElemStyle(w, false)) {
+                if (w.isClosed() && ElemStyles.hasAreaElemStyle(w, false)) {
                     final JsonArrayBuilder container = Json.createArrayBuilder().add(array);
                     geomObj.add("type", "Polygon");