Index: trunk/src/org/openstreetmap/josm/tools/Geometry.java
===================================================================
--- trunk/src/org/openstreetmap/josm/tools/Geometry.java	(revision 15939)
+++ trunk/src/org/openstreetmap/josm/tools/Geometry.java	(revision 15942)
@@ -30,5 +30,4 @@
 import org.openstreetmap.josm.data.osm.INode;
 import org.openstreetmap.josm.data.osm.IPrimitive;
-import org.openstreetmap.josm.data.osm.IRelation;
 import org.openstreetmap.josm.data.osm.IWay;
 import org.openstreetmap.josm.data.osm.MultipolygonBuilder;
@@ -563,5 +562,6 @@
             return Geometry.getArea(((Way) p).getNodes());
         }
-        if (p.isMultipolygon() && !p.isIncomplete() && !((IRelation<?>) p).hasIncompleteMembers()) {
+        if (p instanceof Relation && p.isMultipolygon() && !p.isIncomplete()
+                && !((Relation) p).hasIncompleteMembers()) {
             Multipolygon mp = MultipolygonCache.getInstance().get((Relation) p);
             Path2D path = new Path2D.Double();