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

```ts
const assertNonNullable: <T>(
  value: T,
  message?: string,
) => asserts value is NonNullable<T>;
```

Defined in: [packages/common/src/Assert.ts:318](https://github.com/evoluhq/evolu/blob/037c390af081e9944d616ff298a729515c5c5ab7/packages/common/src/Assert.ts#L318)

Asserts that a value is non-nullable.

Following TypeScript's [NonNullable](https://www.typescriptlang.org/docs/handbook/utility-types.html#nonnullabletype), non-nullable here means neither
null nor undefined. Use this when a value is logically guaranteed to be
non-nullable but TypeScript cannot prove it.