diff -r 8c14a9f0c232 -r 787578f33c21 rt/vm/src/main/java/org/apidesign/vm4brwsr/ByteCodeToJavaScript.java
--- a/rt/vm/src/main/java/org/apidesign/vm4brwsr/ByteCodeToJavaScript.java	Mon Mar 25 13:33:03 2013 +0100
+++ b/rt/vm/src/main/java/org/apidesign/vm4brwsr/ByteCodeToJavaScript.java	Wed Apr 10 10:08:18 2013 +0200
@@ -1940,7 +1940,7 @@
         final String type = jc.getClassName(indx);
         if (!type.startsWith("[")) {
             emit(out,
-                 "if (@1 !== null && !@1.$instOf_@2) throw {};",
+                 "if (@1 !== null && !@1.$instOf_@2) throw vm.java_lang_ClassCastException(true);",
                  smapper.getA(0), type.replace('/', '_'));
         } else {
             emit(out, "vm.java_lang_Class(false).forName__Ljava_lang_Class_2Ljava_lang_String_2('@2').cast__Ljava_lang_Object_2Ljava_lang_Object_2(@1);",