# Gateway Upgrade Version 3 to 4


## Migration from BinaryFormatter

> [!WARNING]
> When migrating from the `BinaryFormatter` ensure that all endpoints on all sites are updated to use the newly selected data bus deserializer.

The `BinaryFormatter` is being phased out by Microsoft. The data bus configuration API now requires a serializer.

Refer to the [Migration from BinaryFormatter](/nservicebus/upgrades/7to8/databus.md#migration-from-binaryformatter) for details.