Index: applications/editors/josm/plugins/merge-overlap/src/mergeoverlap/MergeOverlapAction.java
===================================================================
--- applications/editors/josm/plugins/merge-overlap/src/mergeoverlap/MergeOverlapAction.java	(revision 30783)
+++ applications/editors/josm/plugins/merge-overlap/src/mergeoverlap/MergeOverlapAction.java	(revision 30784)
@@ -227,5 +227,5 @@
         List<Way> del = new LinkedList<>();
         for (Way w : deletes) {
-            if (!w.isDeleted()) {
+            if (w.getDataSet() != null && !w.isDeleted()) {
                 del.add(w);
             }