diff --git a/core/AmArg.h b/core/AmArg.h
index a0dc91c2..4c97448f 100644
--- a/core/AmArg.h
+++ b/core/AmArg.h
@@ -76,6 +76,7 @@ ArgBlob()
 
 /** \brief variable type argument for DynInvoke APIs */
 class AmArg
+: public ArgObject
 {
  public:
   // type enum