Index: /trunk/src/org/openstreetmap/josm/gui/io/DownloadOpenChangesetsTask.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/io/DownloadOpenChangesetsTask.java	(revision 12011)
+++ /trunk/src/org/openstreetmap/josm/gui/io/DownloadOpenChangesetsTask.java	(revision 12012)
@@ -78,10 +78,12 @@
         }
         if (changesets.isEmpty()) {
-            JOptionPane.showMessageDialog(
-                    Main.parent,
-                    tr("There are no open changesets"),
-                    tr("No open changesets"),
-                    JOptionPane.INFORMATION_MESSAGE
-            );
+            if (!GraphicsEnvironment.isHeadless()) {
+                JOptionPane.showMessageDialog(
+                        Main.parent,
+                        tr("There are no open changesets"),
+                        tr("No open changesets"),
+                        JOptionPane.INFORMATION_MESSAGE
+                );
+            }
             return;
         }