Index: trunk/src/org/openstreetmap/josm/Main.java
===================================================================
--- trunk/src/org/openstreetmap/josm/Main.java	(revision 11207)
+++ trunk/src/org/openstreetmap/josm/Main.java	(revision 11208)
@@ -89,4 +89,5 @@
 import org.openstreetmap.josm.gui.progress.ProgressMonitorExecutor;
 import org.openstreetmap.josm.gui.tagging.presets.TaggingPresets;
+import org.openstreetmap.josm.gui.util.GuiHelper;
 import org.openstreetmap.josm.gui.util.RedirectInputMap;
 import org.openstreetmap.josm.io.FileWatcher;
@@ -804,5 +805,7 @@
      */
     public static boolean exitJosm(boolean exit, int exitCode, SaveLayersDialog.Reason reason) {
-        if (SaveLayersDialog.saveUnsavedModifications(getLayerManager().getLayers(), reason != null ? reason : SaveLayersDialog.Reason.EXIT)) {
+        final boolean proceed = Boolean.TRUE.equals(GuiHelper.runInEDTAndWaitAndReturn(() ->
+                SaveLayersDialog.saveUnsavedModifications(getLayerManager().getLayers(), reason != null ? reason : SaveLayersDialog.Reason.EXIT)));
+        if (proceed) {
             if (Main.main != null) {
                 Main.main.shutdown();