One of the release notes for 4.0.0 is support for typescript v4, so as a user I'd expect to be able to use typescript 4 with react-scripts 4.0.0. Case: package.json with react-scripts 4.0.0 and typescript 4.0.3 with npm on latest (7.0.5) Result:  Expected: No error Fallback: Use ts 3.9.7