# X-Api-Version header is required on new DatoCMS projects

[date: 2022-05-31T15:11:15.944+02:00]

Up until now, if you did not provide an [`X-Api-Version` header](https://www.datocms.com/docs/content-management-api/api-versioning.md) in your request towards the Content Management API, legacy API version 1 was used.

To avoid ambiguity and possible unexpected problems, we have decided to change this behavior on projects created from this point on:

-   if your project was created before 31 May 2022, 13:00:00: not explicitly passing the `X-Api-Version` header will default to CMA API version 1 — nothing changes;
-   if your project is created after 31 May 2022, 13:00:00: not explicitly passing the `X-Api-Version` header will result in an error and a `422 Unprocessable Entity` status code.