diff -r 21da8e2f5911 -r aef4fd91e99c vm/src/main/java/org/apidesign/vm4brwsr/VM.java
--- a/vm/src/main/java/org/apidesign/vm4brwsr/VM.java	Thu Jan 03 16:20:21 2013 +0100
+++ b/vm/src/main/java/org/apidesign/vm4brwsr/VM.java	Thu Jan 10 20:15:11 2013 +0100
@@ -124,7 +124,13 @@
             + "      return vm.org_apidesign_vm4brwsr_VMLazy(false).\n"
             + "        load__Ljava_lang_Object_2Ljava_lang_Object_2Ljava_lang_String_2_3Ljava_lang_Object_2(loader, name, args);\n"
             + "    }\n"
-            + "    if (args[0]) vm.loadClass = loader.loadClass;\n"
+            + "    if (args[0]) {\n"
+            + "      vm.loadClass = loader.loadClass;\n"
+            + "      vm.loadBytes = function(name) {\n"
+            + "        if (!args[0]) throw 'bck2brwsr initialized without loader function, cannot load ' + name;\n"
+            + "        return args[0](name);\n"
+            + "      }\n"
+            + "    }\n"
             + "    return loader;\n"
             + "  };\n");
         out.append("}(this));");