diff --git a/pybind11_protobuf/native_proto_caster.h b/pybind11_protobuf/native_proto_caster.h
index dfdce39..df9d54a 100644
--- a/pybind11_protobuf/native_proto_caster.h
+++ b/pybind11_protobuf/native_proto_caster.h
@@ -91,6 +91,16 @@ struct type_caster<
     : public pybind11_protobuf::proto_caster<
           ProtoType, pybind11_protobuf::native_cast_impl> {};
 
+template <typename ProtoType>
+struct copyable_holder_caster_shared_ptr_with_smart_holder_support_enabled<
+    ProtoType, enable_if_t<std::is_base_of<::google::protobuf::Message, ProtoType>::value>>
+    : std::false_type {};
+
+template <typename ProtoType>
+struct move_only_holder_caster_unique_ptr_with_smart_holder_support_enabled<
+    ProtoType, enable_if_t<std::is_base_of<::google::protobuf::Message, ProtoType>::value>>
+    : std::false_type {};
+
 // NOTE: If smart_holders becomes the default we will need to change this to
 //    type_caster<std::unique_ptr<ProtoType, D>, ...
 // Until then using that form is ambiguous due to the existing specialization