Index: /trunk/src/org/openstreetmap/josm/actions/SaveActionBase.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/actions/SaveActionBase.java	(revision 13114)
+++ /trunk/src/org/openstreetmap/josm/actions/SaveActionBase.java	(revision 13115)
@@ -21,4 +21,5 @@
 import org.openstreetmap.josm.gui.layer.Layer;
 import org.openstreetmap.josm.gui.layer.OsmDataLayer;
+import org.openstreetmap.josm.gui.util.GuiHelper;
 import org.openstreetmap.josm.gui.widgets.AbstractFileChooser;
 import org.openstreetmap.josm.spi.preferences.Config;
@@ -105,6 +106,7 @@
             }
             if (!exported) {
-                JOptionPane.showMessageDialog(Main.parent, tr("No Exporter found! Nothing saved."), tr("Warning"),
-                        JOptionPane.WARNING_MESSAGE);
+                GuiHelper.runInEDTAndWait(() ->
+                    JOptionPane.showMessageDialog(Main.parent, tr("No Exporter found! Nothing saved."), tr("Warning"),
+                        JOptionPane.WARNING_MESSAGE));
                 return false;
             } else if (canceled) {
Index: /trunk/src/org/openstreetmap/josm/gui/io/LayerNameAndFilePathTableCell.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/io/LayerNameAndFilePathTableCell.java	(revision 13114)
+++ /trunk/src/org/openstreetmap/josm/gui/io/LayerNameAndFilePathTableCell.java	(revision 13115)
@@ -26,4 +26,5 @@
 
 import org.openstreetmap.josm.actions.SaveActionBase;
+import org.openstreetmap.josm.gui.layer.NoteLayer;
 import org.openstreetmap.josm.gui.util.CellEditorSupport;
 import org.openstreetmap.josm.gui.widgets.JosmTextField;
@@ -49,4 +50,5 @@
 
     private final transient CellEditorSupport cellEditorSupport = new CellEditorSupport(this);
+    private String extension = "osm";
     private File value;
 
@@ -90,4 +92,5 @@
           .append(addLblLayerName(info));
         if (info.isSavable()) {
+            extension = info.getLayer() instanceof NoteLayer ? "osn" : "osm";
             add(btnFileChooser, GBC.std());
             sb.append("<br>")
@@ -111,4 +114,5 @@
 
         if (info.isSavable()) {
+            extension = info.getLayer() instanceof NoteLayer ? "osn" : "osm";
             add(btnFileChooser, GBC.std());
             add(tfFilename, GBC.eol().fill(GBC.HORIZONTAL).insets(1, 0, 0, 0));
@@ -242,5 +246,5 @@
         @Override
         public void actionPerformed(ActionEvent e) {
-            File f = SaveActionBase.createAndOpenSaveFileChooser(tr("Select filename"), "osm");
+            File f = SaveActionBase.createAndOpenSaveFileChooser(tr("Select filename"), extension);
             if (f != null) {
                 tfFilename.setText(f.toString());