Index: /trunk/src/org/openstreetmap/josm/actions/RestartAction.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/actions/RestartAction.java	(revision 13232)
+++ /trunk/src/org/openstreetmap/josm/actions/RestartAction.java	(revision 13233)
@@ -158,5 +158,5 @@
                 cmd.add("-cp");
                 cmd.add('"' + System.getProperty("java.class.path") + '"');
-                cmd.add(mainCommand[0]);
+                cmd.add(mainCommand[0].replace("jdk.plugin/", "")); // Main class appears to be invalid on Java WebStart 9
             }
             // add JNLP file.