Index: trunk/src/org/openstreetmap/josm/io/OsmReader.java
===================================================================
--- trunk/src/org/openstreetmap/josm/io/OsmReader.java	(revision 2484)
+++ trunk/src/org/openstreetmap/josm/io/OsmReader.java	(revision 2497)
@@ -563,7 +563,12 @@
 
             progressMonitor.subTask(tr("Preparing data set..."));
-            reader.processNodesAfterParsing();
-            reader.processWaysAfterParsing();
-            reader.processRelationsAfterParsing();
+            reader.ds.beginUpdate();
+            try {
+                reader.processNodesAfterParsing();
+                reader.processWaysAfterParsing();
+                reader.processRelationsAfterParsing();
+            } finally {
+                reader.ds.endUpdate();
+            }
             progressMonitor.worked(1);
             return reader.getDataSet();