JavaUtil.diff

diff --git a/src/org/jruby/javasupport/JavaUtil.java b/src/org/jruby/javasupport/JavaUtil.java
index e8de4c4..eb0842e 100644
--- a/src/org/jruby/javasupport/JavaUtil.java
+++ b/src/org/jruby/javasupport/JavaUtil.java
@@ -868,6 +868,8 @@ public class JavaUtil {
     public static Object convertArgumentToType(ThreadContext context, IRubyObject arg, Class target) {
         if (arg instanceof JavaObject) {
             return coerceJavaObjectToType(context, ((JavaObject)arg).getValue(), target);
+        } else if (arg.respondsTo("java_object")) {
+            return convertArgumentToType(context, arg.callMethod(context, "java_object"), target);
         } else if (arg.dataGetStruct() instanceof JavaObject) {
             JavaObject innerWrapper = (JavaObject)arg.dataGetStruct();