src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/codegen/SpillObjectCreator.java

@@ -187,11 +187,12 @@
         return propertyMap;
     }
 
     @Override
     protected void loadValue(final Expression expr, final Type type) {
-        codegen.loadExpressionAsType(expr, type);
+        // Use generic type in order to avoid conversion between object types
+        codegen.loadExpressionAsType(expr, Type.generic(type));
     }
 
     @Override
     protected Class<? extends ScriptObject> getAllocatorClass() {
         return codegen.useDualFields() ? JD.class : JO.class;