diff -r 3b960d9631b2 -r fd3a354d6e8f rt/vm/src/main/java/org/apidesign/vm4brwsr/VM.java
--- a/rt/vm/src/main/java/org/apidesign/vm4brwsr/VM.java	Sun Nov 09 06:54:07 2014 +0100
+++ b/rt/vm/src/main/java/org/apidesign/vm4brwsr/VM.java	Sun Nov 09 10:36:08 2014 +0100
@@ -235,11 +235,7 @@
                 while (resource.startsWith("/")) {
                     resource = resource.substring(1);
                 }
-                InputStream emul = resources.get(resource);
-                if (emul == null) {
-                    throw new IOException("Can't find " + resource);
-                }
-                readResource(emul, this);
+                requireResourceImpl(resource);
                 asBinary.remove(resource);
             }
             scripts = new StringArray();
@@ -260,6 +256,14 @@
         }
     }
 
+    final void requireResourceImpl(String resource) throws IOException {
+        InputStream emul = resources.get(resource);
+        if (emul == null) {
+            throw new IOException("Can't find " + resource);
+        }
+        readResource(emul, this);
+    }
+
     private static void readResource(InputStream emul, Appendable out) throws IOException {
         try {
             int state = 0;
@@ -703,6 +707,11 @@
             out.append("\n  return vm.").append(cls).append("(instance);");
             out.append("\n}");
         }
+
+        @Override
+        protected void requireResource(String resourcePath) throws IOException {
+            requireResourceImpl(resourcePath);
+        }
     }
 
     private static final class Extension extends VM {
@@ -795,5 +804,10 @@
             out.append(cls).append(" = f;})(instance);");
             out.append("\n}");
         }
+
+        @Override
+        protected void requireResource(String resourcePath) throws IOException {
+            requireResourceImpl(resourcePath);
+        }
     }
 }