# MobX 6.1.5

- Product: MobX (https://whatsnew.fyi/product/mobx)
- Vendor: MobX
- Date: 2021-02-04
- Version: 6.1.5
- Original notes: https://github.com/mobxjs/mobx/releases/tag/mobx%406.1.5
- Permalink: https://whatsnew.fyi/product/mobx/releases/6.1.5

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

Reuse: the summaries, labels and curation here are © What's New. Quote freely with attribution and a link back; wholesale republication of the corpus is not permitted — terms: https://whatsnew.fyi/terms. The vendors' own release notes remain their publishers'.

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- **changed** — Optimize decorators
- **added** — Add warning for extending builtins
- **changed** — Use globalThis in global detection
- **fixed** — makeAutoObservable now works properly with symbolic keys
- **fixed** — isComputedProp and getAtom second argument type is now compatible with Symbols

###### Patch Changes

-   [`3979bee3`](https://github.com/mobxjs/mobx/commit/3979bee36c82d342050978834197ea15a7ddbbf8) [#2773](https://github.com/mobxjs/mobx/pull/2773) Thanks [@urugator](https://github.com/urugator)! - Decorators optimization


-   [`7820e5ea`](https://github.com/mobxjs/mobx/commit/7820e5eae0c9dcdfa1e69cf92e0bfa209b2b478b) [#2769](https://github.com/mobxjs/mobx/pull/2769) Thanks [@iChenLei](https://github.com/iChenLei)! - add warn for extending builtins


-   [`a7c15171`](https://github.com/mobxjs/mobx/commit/a7c1517133915c2891e92a865fe5475627b6b89f) [#2775](https://github.com/mobxjs/mobx/pull/2775) Thanks [@pkit](https://github.com/pkit)! - use globalThis in global detection


-   [`5d41b646`](https://github.com/mobxjs/mobx/commit/5d41b6462cf609df869a088e353bc485846c88f8) [#2774](https://github.com/mobxjs/mobx/pull/2774) Thanks [@urugator](https://github.com/urugator)! - Fix: `makeAutoObservable` now working properly with symbolic keys
    Fix: `isComputedProp` and `getAtom` second arg type is incompatible with Symbols