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

```ts
type NewKeys<T, Existing> = {
  [K in keyof T]: K extends keyof Existing ? never : T[K];
};
```

Defined in: [packages/common/src/Types.ts:368](https://github.com/evoluhq/evolu/blob/e7144e2bbe9069362b62dec1b64a8aa922b8f1b0/packages/common/src/Types.ts#L368)

Constrains `T` to only contain keys not present in `Existing`.

Use as a generic constraint to prevent overriding existing properties.