# FirstEmissionBlockNumberAlreadySet (/docs/errors/chain/FirstEmissionBlockNumberAlreadySet)

`start_call` was issued for a subnet whose emissions have already been started. Check the `FirstEmissionBlockNumber` storage for the netuid; a non-empty value means the subnet is already emitting and no action is needed.

Declared by the `SubtensorModule` pallet; it classifies to the semantic code [`already_exists`](/docs/errors/already-exists).

## Remediation [#remediation]

The object or state already exists; treat the goal as met or pick a different target

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