# MultiBlockMigrationsOngoing (/docs/errors/chain/MultiBlockMigrationsOngoing)

Runtime code replacement is blocked while a multi-block migration is still executing. Wait for the ongoing migrations to complete (check the multi-block migrations cursor) before retrying `set_code` or the authorized upgrade.

Declared by the `System` pallet; it classifies to the semantic code [`too_early`](/docs/errors/too-early).

## Remediation [#remediation]

The required window has not opened yet; wait some blocks and retry

The same explanation is available in the terminal: `btcli explain MultiBlockMigrationsOngoing`.