diff -r 973e52d4cabb -r 80851e48a68f rt/vm/src/main/java/org/apidesign/vm4brwsr/ByteCodeToJavaScript.java
--- a/rt/vm/src/main/java/org/apidesign/vm4brwsr/ByteCodeToJavaScript.java	Tue Jun 07 06:20:20 2016 +0200
+++ b/rt/vm/src/main/java/org/apidesign/vm4brwsr/ByteCodeToJavaScript.java	Wed Jun 08 06:50:38 2016 +0200
@@ -1823,7 +1823,7 @@
             in.equals("org/netbeans/html/boot/spi/Fn")
         )) {
             mcn = "java_lang_Class";
-        } else if (in.startsWith("net/java/html/lib/") && in.endsWith("/Exports")) {
+        } else if (DirectlLibraries.isScriptLibrary(in) && in.endsWith("/Exports")) {
             append(mi[1]);
             append('(');
             mcn = null;
@@ -2394,6 +2394,13 @@
 
     private void generateInstanceOf(int indx, final StackMapper smapper) throws IOException {
         String type = jc.getClassName(indx);
+        if (DirectlLibraries.isScriptLibrary(type)) {
+            emit(smapper, this,
+                    "var @2 = @1 !== null && @1 !== undefined",
+                 smapper.popA(), smapper.pushI(),
+                 mangleClassName(type));
+            return;
+        }
         if (!type.startsWith("[")) {
             emit(smapper, this, 
                     "var @2 = @1 != null && @1['$instOf_@3'] ? 1 : 0;",
@@ -2424,6 +2431,12 @@
 
     private void generateCheckcast(int indx, final StackMapper smapper) throws IOException {
         String type = jc.getClassName(indx);
+        if (DirectlLibraries.isScriptLibrary(type)) {
+            emitNoFlush(smapper,
+                 "",
+                 smapper.getT(0, VarType.REFERENCE, false), mangleClassName(type), type.replace('/', '.'));
+            return;
+        }
         if (!type.startsWith("[")) {
             emitNoFlush(smapper, 
                  "if (@1 !== null && !@1['$instOf_@2']) vm.java_lang_Class(false).castEx(@1, '@3');",