Index: /trunk/src/org/openstreetmap/josm/data/Preferences.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/data/Preferences.java	(revision 8815)
+++ /trunk/src/org/openstreetmap/josm/data/Preferences.java	(revision 8816)
@@ -1483,5 +1483,5 @@
         Utils.updateSystemProperty("user.language", get("language"));
         // Workaround to fix a Java bug.
-        // Force AWT toolkit to update its internal preferences (fix #3645).
+        // Force AWT toolkit to update its internal preferences (fix #6345).
         // This ugly hack comes from Sun bug database: https://bugs.openjdk.java.net/browse/JDK-6292739
         try {
@@ -1489,6 +1489,8 @@
             field.setAccessible(true);
             field.set(null, ResourceBundle.getBundle("sun.awt.resources.awt"));
-        } catch (Exception e) {
-            // Ignore all exceptions
+        } catch (Exception | InternalError e) {
+            // Ignore all exceptions, including internal error raised by Java 9 Jigsaw EA:
+            // java.lang.InternalError: legacy getBundle can't be used to find sun.awt.resources.awt in module java.desktop
+            // InternalError catch to remove when https://bugs.openjdk.java.net/browse/JI-9025152 is resolved
             if (Main.isTraceEnabled()) {
                 Main.trace(e.getMessage());