---
title: "Migration to Agda 2.7.0"
---

We upgraded to [Agda 2.7.0][agda-2.7.0] and [version 2.1 of the standard library][agda-stdlib-v2.1].
If you want to continue working with the book, you'll have to update your versions locally.
Please follow the instructions in [Getting Started](/GettingStarted/) to reinstall Agda and the standard library.

In the past, we maintained compatibility with versions of Agda all the way back to [Agda 2.6.1.3][agda-2.6.1.3] and [version 1.6 of the standard library][agda-stdlib-v1.6].
However, [version 2.0 of the standard library][agda-stdlib-v2.0] broke backwards compatibility with earlier versions of the standard library.
Consequently, starting with today's version of PLFA, the oldest supported versions of Agda and its standard library are [Agda 2.6.4.3][agda-2.6.4.3] and [version 2.0 of the standard library][agda-stdlib-v2.0].

[agda-stdlib-v1.6]: https://github.com/agda/agda-stdlib/releases/tag/v1.6
  "Agda standard library version 1.6 on GitHub"
[agda-stdlib-v2.0]: https://github.com/agda/agda-stdlib/releases/tag/v2.0
  "Agda standard library version 2.0 on GitHub"
[agda-stdlib-v2.1]: https://github.com/agda/agda-stdlib/releases/tag/v2.1
  "Agda standard library version 2.1 on GitHub"
[agda-2.6.1.3]: https://github.com/agda/agda/releases/tag/v2.6.1.3
  "Agda version 2.6.1.3 on GitHub"
[agda-2.6.4.3]: https://github.com/agda/agda/releases/tag/v2.6.4.3
  "Agda version 2.6.4.3 on GitHub"
[agda-2.7.0]: https://github.com/agda/agda/releases/tag/v2.7.0
  "Agda version 2.7.0 on GitHub"