diff --git a/src/DataTypeList.cpp b/src/DataTypeList.cpp
index 703e760..6b6c8ac 100644
--- a/src/DataTypeList.cpp
+++ b/src/DataTypeList.cpp
@@ -44,7 +44,7 @@ void DataTypeList::finiVal(ValRef &v) {
 }
 
 ValRef DataTypeList::copyVal(const ValRef &src) {
-
+    return ValRef();
 }
 
 IModelField *DataTypeList::mkRootField(