Index: trunk/src/org/openstreetmap/josm/actions/RestartAction.java
===================================================================
--- trunk/src/org/openstreetmap/josm/actions/RestartAction.java	(revision 13392)
+++ trunk/src/org/openstreetmap/josm/actions/RestartAction.java	(revision 13393)
@@ -137,4 +137,7 @@
         // program main and program arguments (be careful a sun property. might not be supported by all JVM)
         final String javaCommand = System.getProperty("sun.java.command");
+        if (javaCommand == null) {
+            throw new IOException("Unable to retrieve sun.java.command property");
+        }
         String[] mainCommand = javaCommand.split(" ");
         if (javaCommand.endsWith(".jnlp") && jnlp == null) {