[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) › MapError

```ts
type MapError<KeyError, ValueError, Collision> =
  | MapNotMapError
  | MapEntriesErrorValue<
      KeyError,
      ValueError,
      Collision | MapExcessPropertyIssue
    >;
```

Defined in: [packages/common/src/Type.ts:9812](https://github.com/evoluhq/evolu/blob/dd96d79f1dbe9a49fa12ce8e0aa7d3d0177795ca/packages/common/src/Type.ts#L9812)

Error returned while validating a [map](https://evolu.dev/docs/api-reference/common/Type/functions/map) and its entries.