--- old/src/share/vm/prims/whitebox.cpp	2012-06-21 13:24:13.000000000 +0200
+++ new/src/share/vm/prims/whitebox.cpp	2012-06-21 13:24:13.000000000 +0200
@@ -113,6 +113,9 @@
   int offset = offset_for_field(field_name, object,
       vmSymbols::string_signature());
   oop string = object->obj_field(offset);
+  if (oopDesc::is_null(string)) {
+    return NULL;
+  }
   const char* ret = java_lang_String::as_utf8_string(string);
   return ret;
 }