# Fleet indices prevent upgrade to Elasticsearch 9 **URL:** \ **Category:** Elasticsearch\ **Created:** [June 9, 2025, 3:21pm UTC](https://discuss.elastic.co/t/fleet-indices-prevent-upgrade-to-elasticsearch-9/379006 "2025-06-09T15:21:19Z")\ **Posts on this page:** 1\ **Showing post:** 4
**Author:** ![RainTown](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/raintown/32/140206_2.png) [@RainTown](https://discuss.elastic.co/u/RainTown)\ **Post date:** [June 10, 2025, 8:58am UTC](https://discuss.elastic.co/t/fleet-indices-prevent-upgrade-to-elasticsearch-9/379006/4 "2025-06-10T08:58:50Z")
> [@sparkblaze](#): > > Interesting, I clearly suck at searching for similar issues, I did have a look (albeit via Google), but didn't find any about upgrading to v9... It wasn't a criticism of you, "why didn't you search:" sort of thing. Rather the opposite. To give an example > [@Issues with upgrade from 8.18.1 to 9.0.1](https://discuss.elastic.co/t/issues-with-upgrade-from-8-18-1-to-9-0-1/378753): > > Hello, I'm trying to upgrade current 8.18.1 to 9.0.1 but facing a lot of issues, Most of them have compatibility issues preventing upgrade. For example everytime I'm receiving something like below: "error.stack\_trace":"java.lang.IllegalStateException: The index [.reporting-2021.10.03/7qFTO5dhTDm4fdsinJ1kQw] created in version [7.8.0] with current compatibility version [7.8.0] must be marked as read-only using the setting [index.blocks.write] set to [true] before upgrading to 9.0.1 From my… had a not dis-similar story. > [@sparkblaze](#): > > turns out this was entirely of my own making I think thats _maybe_ a little unfair on yourself. > [@sparkblaze](#): > > I think that if any improvements were to be proposed, then making "Migrate system indices" behave more similarly to "Review deprecated settings and resolve issues" and have a clear numeric indicators of how many indices need migrating etc, then that feels like a decent improvement. IMO thats a great idea. > [@sparkblaze](#): > > I did run into an IllegalStateException error for .async-search which was because I had a legacy index template (from v6 or so) to stretch the number of shards for indices like .kibana and .security across all the cluster nodes and this was preventing the system indices from doing their upgrades. Yes, I dont think many people would have done that, so it might make things more complex. Thanks for the feedback and great that you resolved your issue. --- _[View the full topic](https://discuss.elastic.co/t/fleet-indices-prevent-upgrade-to-elasticsearch-9/379006)._