When testing my runtime upgrade from polkadot_v1.0.0 to 1.5.0 with try-runtime I get this error from try-runtime

[2024-02-06T14:50:51Z ERROR runtime::executive] - 0. error: Failed to decode storage item `ParachainSystem::HostConfiguration`

Enabling debug info reveals the offending key 0x45323df7cc47150b3930e2666b0aa313c522231880238a0c56021b8744a00743 also known as parachainSystem.hostConfiguration()

Why does try-runtime think this type is ParachainSystem::HostConfiguration, this type is not even included in my build? In polkadot js the type is PolkadotPrimitivesV5AbridgedHostConfiguration before the upgrade and v6 after.

When I delete the storage key in the migration the error disappears but will this have any negative side effects?

  • 1
    I observe the same when upgrading from Polkadot-sdk 1.0.0 to 1.6.0
    – brenzi
    Feb 11 at 16:07

1 Answer 1


The error is "expected". When async backing was merged, the HostConfiguration type changed. The AbridgedHostConfiguration is, as the name suggests, an abridged version of the HostConfiguration. Basically it only includes the elements that are relevant for the parachain side. There was no migration added for this storage entry, because this storage entry is overridden by the set_validation_data inherent in each block. So, you can ignore this error.

  • Yep. The error should go away on its own after the next runtime upgrade, should open another issue if it doesn't.
    – liamaharon
    Feb 12 at 12:03
  • We start to get into the mindset, if there is an error in try-runtime we should fix it not ignore it, so if this kind of false positives are common it is problematic for this work flow.
    – Simson
    Feb 12 at 23:30
  • Yeah it sucks. This should be a one-off occurrence we couldn't avoid due to how the HostConfig stuff works. In the future should not happen again.
    – liamaharon
    Feb 13 at 1:47

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