diff --git a/Runtime/MkCastTo.py b/Runtime/MkCastTo.py
index 9c7d7e45e..97c114642 100644
--- a/Runtime/MkCastTo.py
+++ b/Runtime/MkCastTo.py
@@ -125,7 +125,7 @@ public:
 
 for tp in CENTITY_TYPES:
     if type(tp) == tuple:
-        headerf.write('  void Visit(%s* p);\n' % getqualified(tp))
+        headerf.write('  void Visit(%s* p) override;\n' % getqualified(tp))
 
 headerf.write('''
   T* GetPtr() const { return ptr; }