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## [0.17.1](https://www.npmjs.com/package/@sinclair/typebox/v/0.17.1)
- Remove default `additionalProperties: false` constraint from all object schemas.
This update removes the `additionalProperties: false` constraint on all object schemas. This constraint was introduced on `0.16.x` but has resulted in significant downstream problems composing schemas whose types `intersect`. This is due to a JSON schema design principle where constraints should only be added (never removed), and that intersection types may require removal of the `additionalProperties` constraint in some cases, this had resulted in some ambiguity with respect to how TypeBox should handle such intersections.
This update can also be seen as a precursor towards TypeBox potentially leveraging `unevaluatedProperties` for type intersection in future releases. Implementers should take note that in order to constrain the schema to known properties, one should apply the `additionalProperties: false` as the second argument to `Type.Object({...})`.
```typescript
const T = Type.Object({
a: Type.String(),
b: Type.Number()
}, {
additionalProperties: false
})
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