Index: trunk/src/org/openstreetmap/josm/data/osm/SimplePrimitiveId.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/osm/SimplePrimitiveId.java	(revision 3114)
+++ trunk/src/org/openstreetmap/josm/data/osm/SimplePrimitiveId.java	(revision 3115)
@@ -2,6 +2,7 @@
 package org.openstreetmap.josm.data.osm;
 
-public class SimplePrimitiveId implements PrimitiveId {
+import java.io.Serializable;
 
+public class SimplePrimitiveId implements PrimitiveId, Serializable {
     private final long id;
     private final OsmPrimitiveType type;