diff --git a/src/share/vm/classfile/classLoaderData.inline.hpp b/src/share/vm/classfile/classLoaderData.inline.hpp
index 11014f25cbb74d71c00de3b08f89da757a1422d3..755ac54a9f9747f2777822a83d4be175bee08df4 100644
--- a/src/share/vm/classfile/classLoaderData.inline.hpp
+++ b/src/share/vm/classfile/classLoaderData.inline.hpp
@@ -40,7 +40,7 @@ inline ClassLoaderData* ClassLoaderData::class_loader_data(oop loader) {
 
 
 inline ClassLoaderData *ClassLoaderDataGraph::find_or_create(Handle loader, TRAPS) {
-  assert(loader() != NULL,"Must be a class loader");
+  guarantee(loader() != NULL && loader()->is_oop(), "Loader must be oop");
   // Gets the class loader data out of the java/lang/ClassLoader object, if non-null
   // it's already in the loader_data, so no need to add
   ClassLoaderData* loader_data= java_lang_ClassLoader::loader_data(loader());