[API reference](https://evolu.dev/docs/api-reference) › [@evolu/common](https://evolu.dev/docs/api-reference/common) › [Type](https://evolu.dev/docs/api-reference/common/Type) › MapKeyIssue

```ts
type MapKeyIssue<Error> = Error extends TypeError
  ? {
      error: Error;
      index: number;
      key: unknown;
      kind: "Key";
    }
  : never;
```

Defined in: [packages/common/src/Type.ts:8621](https://github.com/evoluhq/evolu/blob/037c390af081e9944d616ff298a729515c5c5ab7/packages/common/src/Type.ts#L8621)

An invalid key and its entry index in a [map](https://evolu.dev/docs/api-reference/common/Type/functions/map).