# Engine Errors

## `Engine.AsyncScopeError`

Thrown when [`Engine.with`](/wasm/crypto/Engine/with) is given an asynchronous function.

**Source:** [src/core/Engine.ts](https://github.com/wevm/ox/blob/main/src/core/Engine.ts#L297)

## `Engine.InvalidSlotValueError`

Thrown when an engine slot is not an object or `undefined`.

**Source:** [src/core/Engine.ts](https://github.com/wevm/ox/blob/main/src/core/Engine.ts#L261)

## `Engine.UnknownPrimitiveError`

Thrown when a slot is given an unrecognized primitive name.

**Source:** [src/core/Engine.ts](https://github.com/wevm/ox/blob/main/src/core/Engine.ts#L281)

## `Engine.UnknownSlotError`

Thrown when an unrecognized engine slot is supplied.

**Source:** [src/core/Engine.ts](https://github.com/wevm/ox/blob/main/src/core/Engine.ts#L270)