Index: /trunk/src/org/openstreetmap/josm/gui/datatransfer/importers/PrimitiveTagTransferPaster.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/datatransfer/importers/PrimitiveTagTransferPaster.java	(revision 12719)
+++ /trunk/src/org/openstreetmap/josm/gui/datatransfer/importers/PrimitiveTagTransferPaster.java	(revision 12720)
@@ -42,5 +42,8 @@
     public boolean importTagsOn(TransferSupport support, Collection<? extends OsmPrimitive> selection)
             throws UnsupportedFlavorException, IOException {
-        PrimitiveTagTransferData data = (PrimitiveTagTransferData) support.getTransferable().getTransferData(df);
+        Object o = support.getTransferable().getTransferData(df);
+        if (!(o instanceof PrimitiveTagTransferData))
+            return false;
+        PrimitiveTagTransferData data = (PrimitiveTagTransferData) o;
 
         TagPasteSupport tagPaster = new TagPasteSupport(data, selection);