diff -r 958a3b7fad36 -r de609e0cdab5 rt/vm/src/test/java/org/apidesign/vm4brwsr/LibUse.java
--- a/rt/vm/src/test/java/org/apidesign/vm4brwsr/LibUse.java	Wed Jun 08 07:15:54 2016 +0200
+++ b/rt/vm/src/test/java/org/apidesign/vm4brwsr/LibUse.java	Fri Jun 10 05:52:44 2016 +0200
@@ -17,7 +17,9 @@
  */
 package org.apidesign.vm4brwsr;
 
+import static net.java.html.lib.Exports.NaN;
 import static net.java.html.lib.Exports.eval;
+import static net.java.html.lib.Exports.isNaN;
 import static net.java.html.lib.Exports.parseInt;
 import net.java.html.lib.Objs;
 
@@ -50,4 +52,9 @@
         return parseInt(str, radix);
     }
 
+    public boolean checkNaN() throws Exception {
+        double nan = NaN;
+        return isNaN(nan);
+    }
+
 }