# custom

`import { custom } from "destack:simulation/fault";`

Create a user-defined simulation fault.

```ds title="custom"
export function custom(name: string, payload?: unknown | undefined): CustomFault
```

[language/library/src/simulation/fault/fault.ds:551:553](https://github.com/destack-sh/destack/blob/main/language/library/src/simulation/fault/fault.ds#L551-L553)