--- patch123/mojo/public/cpp/bindings/lib/serialization_forward.h	2024-03-13 20:35:52.218509700 +0100
+++ patch123/mojo/public/cpp/bindings/lib/serialization_forward.h.emplace	2024-03-24 20:42:41.726615080 +0100
@@ -69,7 +69,7 @@ bool Deserialize(DataType&& input, Input
                                             ::mojo::DefaultConstruct::Tag>) {
         output->emplace(mojo::internal::DefaultConstructTag());
       } else {
-        output->emplace();
+        output->emplace() = {};
       }
     }
     return Deserialize<MojomType>(std::forward<DataType>(input),