# Backwards compatibility problem when updating from Mender 4.0 to 5.0

**URL:** <https://hub.mender.io/t/backwards-compatibility-problem-when-updating-from-mender-4-0-to-5-0/7839>\
**Category:** General Discussions\
**Tags:** mender-client\
**Created:** [June 18, 2025, 12:29pm UTC](https://hub.mender.io/t/backwards-compatibility-problem-when-updating-from-mender-4-0-to-5-0/7839 "2025-06-18T12:29:37Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![pulkomandy](https://yyz2.discourse-cdn.com/flex036/user_avatar/hub.mender.io/pulkomandy/32/1742_2.png) [@pulkomandy](https://hub.mender.io/u/pulkomandy)\
**Post date:** [June 18, 2025, 12:29pm UTC](https://hub.mender.io/t/backwards-compatibility-problem-when-updating-from-mender-4-0-to-5-0/7839/1 "2025-06-18T12:29:37Z")

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Hello,

We are investigating updating our devices from Mender 4.0 to Mender 5.0. One part of this process is checking if downgrades are possible as we occasionally need to roll back a device to an older version of our software.

While testing this we found the following error:

“Could not fulfill request: Operation not supported: State data has a version which is not supported by this client”

It looks like standalone\_data\_version is changed in 2c1d92212dcdba383ce0872ad108b3f6cde8c0f9, and versions 4.0.x of Mender do not handle the new data version. This leaves the device in a “confused” state when installing a Mender 4.x over a 5.x, it seems we can’t commit the update (and possibly rollback also doesn’t work well, but I will check that with my colleague who did the test).

This seems to not be mentioned in release notes. But, if I understand right it affects only standalone mode (updates through Mender server should be fine), can you confirm that?

Is there a risk that this will cause problems in rollback of an install of 5.0 back to 4.0?

Is there a way to ensure some level of backwards compatibility? For example introduce a 4.0.x version that can read (but not write) the new format, so we can first update to that and only later to 5.0?

In case this matters: we are using the Yocto layer integration with Yocto kirkstone on custom hardware. We are using both standalone mode and online mode depending on the scenario.

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**Author:** ![janaperic](https://yyz2.discourse-cdn.com/flex036/user_avatar/hub.mender.io/janaperic/32/1608_2.png) [@janaperic](https://hub.mender.io/u/janaperic)\
**Post date:** [June 25, 2025, 11:18am UTC](https://hub.mender.io/t/backwards-compatibility-problem-when-updating-from-mender-4-0-to-5-0/7839/2 "2025-06-25T11:18:34Z")

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Hi,

Thank you for your question.

I want to clarify that **Mender does not officially support downgrading the client** or rolling back the client version (e.g., from 5.x to 4.x). This is the reason you’re seeing the `Operation not supported: State data has a version which is not supported by this client` error as Mender 4.x cannot handle the newer state data format introduced in Mender 5.x.

As you noted, this mainly affects standalone deployments; server-managed updates and rollbacks should continue to work as expected, provided the artifact itself is compatible.

There is no backwards compatibility mechanism (e.g., a 4.x client that can read 5.x state data). We strongly recommend planning upgrades in a forward-only direction. If you need rollback of software versions, this should be handled at the application level rather than via client downgrades.

Kind regards,  
Jana