diff -r 61a5c529136c -r 958a3b7fad36 rt/vm/src/test/java/org/apidesign/vm4brwsr/LibUseTest.java
--- a/rt/vm/src/test/java/org/apidesign/vm4brwsr/LibUseTest.java	Wed Jun 08 07:02:46 2016 +0200
+++ b/rt/vm/src/test/java/org/apidesign/vm4brwsr/LibUseTest.java	Wed Jun 08 07:15:54 2016 +0200
@@ -55,4 +55,22 @@
             "Ahoj", "Ahoj"
         );
     }
+
+   @Test
+    public void optionalParams1() throws Exception {
+        code.assertExec(
+            "Fifteen", LibUse.class,
+            "parse__DLjava_lang_String_2",
+            15, "0xF"
+        );
+    }
+
+    @Test
+    public void optionalParams2() throws Exception {
+        code.assertExec(
+            "Fifteen", LibUse.class,
+            "parse__DLjava_lang_String_2I",
+            15, "F", 16
+        );
+    }
 }