Index: trunk/src/org/openstreetmap/josm/actions/SaveActionBase.java
===================================================================
--- trunk/src/org/openstreetmap/josm/actions/SaveActionBase.java	(revision 9686)
+++ trunk/src/org/openstreetmap/josm/actions/SaveActionBase.java	(revision 9687)
@@ -205,6 +205,5 @@
             }
             file = new File(fn);
-            // Confirm overwrite, except for OSX native file dialogs which already ask for confirmation (see #11362)
-            if (!(Main.isPlatformOsx() && FileChooserManager.PROP_USE_NATIVE_FILE_DIALOG.get()) && !confirmOverwrite(file))
+            if (!fc.getSelectedFile().exists() && !confirmOverwrite(file))
                 return null;
         }
Index: trunk/src/org/openstreetmap/josm/gui/widgets/FileChooserManager.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/widgets/FileChooserManager.java	(revision 9686)
+++ trunk/src/org/openstreetmap/josm/gui/widgets/FileChooserManager.java	(revision 9687)
@@ -348,5 +348,6 @@
         }
 
-        if (!open && !SaveActionBase.confirmOverwrite(fc.getSelectedFile())) {
+        if (!open && !FileChooserManager.PROP_USE_NATIVE_FILE_DIALOG.get() &&
+            !SaveActionBase.confirmOverwrite(fc.getSelectedFile())) {
             return null;
         }