# CONFIG\_VALIDATION\_ERROR, Protocol version is not defined

**URL:** <https://forum.canton.network/t/config-validation-error-protocol-version-is-not-defined/7516>\
**Category:** App Development\
**Created:** [November 21, 2024, 1:19pm UTC](https://forum.canton.network/t/config-validation-error-protocol-version-is-not-defined/7516 "2024-11-21T13:19:56Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![WallaceKelly](https://yyz2.discourse-cdn.com/flex034/user_avatar/forum.canton.network/wallacekelly/32/5046_2.png) [@WallaceKelly](https://forum.canton.network/u/WallaceKelly)\
**Post date:** [November 21, 2024, 1:19pm UTC](https://forum.canton.network/t/config-validation-error-protocol-version-is-not-defined/7516/1 "2024-11-21T13:19:56Z")

</div>

When I try to start a 2.9.x Canton domain, I get the following error:

```plaintext
CONFIG_VALIDATION_ERROR(8,0):
Failed to validate the configuration due to:
Protocol version is not defined for domain `mydomain`.
Define protocol version at key
`init.domain-parameters.protocol-version`

```

What is this about? What do I do?

---

<div class="post-metadata">

**Author:** ![WallaceKelly](https://yyz2.discourse-cdn.com/flex034/user_avatar/forum.canton.network/wallacekelly/32/5046_2.png) [@WallaceKelly](https://forum.canton.network/u/WallaceKelly)\
**Post date:** [November 21, 2024, 1:20pm UTC](https://forum.canton.network/t/config-validation-error-protocol-version-is-not-defined/7516/2 "2024-11-21T13:20:02Z")

</div>

The [release notes for 2.9.1](https://blog.digitalasset.com/developers/release-notes/2.9.1#impact-and-migration) say:

> you must now set the protocol version explicitly. In prior releases, the domain protocol version was set to the latest protocol version by default.

This means that if you have a Canton configuration that you were using prior to 2.9.x, you will need to add an additional entry. As the error message says, “Define protocol version at key `init.domain-parameters.protocol-version`.”

For example:

```hocon
canton {
  domains {
    mydomain {
      init.domain-parameters.protocol-version = 5
              :

```

To learn more about Canton protocol versions, see [the docs](https://docs.daml.com/canton/usermanual/versioning.html#protocol-version).