Index: src/org/openstreetmap/josm/gui/layer/AlignImageryPanel.java
===================================================================
--- src/org/openstreetmap/josm/gui/layer/AlignImageryPanel.java	(revision 18934)
+++ src/org/openstreetmap/josm/gui/layer/AlignImageryPanel.java	(working copy)
@@ -11,6 +11,7 @@
 import javax.swing.JButton;
 import javax.swing.JCheckBox;
 import javax.swing.JPanel;
+import javax.swing.SwingUtilities;
 import javax.swing.border.CompoundBorder;
 import javax.swing.border.EmptyBorder;
 import javax.swing.border.EtchedBorder;
@@ -92,7 +93,7 @@
         if (MainApplication.isDisplayingMapView() && showAgain.get() && !infoToAdd.isGeoreferenceValid()
                 && map.getTopPanel(AlignImageryPanel.class) == null) {
             double w = GuiHelper.getScreenSize().getWidth();
-            map.addTopPanel(new AlignImageryPanel(w > 1300, showAgain, infoToAdd));
+            SwingUtilities.invokeLater(() -> map.addTopPanel(new AlignImageryPanel(w > 1300, showAgain, infoToAdd)));
         }
     }
 }