TS2375: exactOptionalPropertyTypes undefined mismatch - in CI

By Kaveh Alemi·Latchkey

With exactOptionalPropertyTypes on, assigning undefined to an optional property is rejected unless the type explicitly allows undefined.

What this error means

Type-checking fails with TS2375 after enabling exactOptionalPropertyTypes, suggesting you add undefined to the target type.

src/opts.ts(6,3): error TS2375: Type '{ label: string | undefined; }' is not assignable to type 'Props' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the type of the target.

Common causes

How to fix it

Add undefined to the property type

1. If undefined is a valid value, declare the property as type | undefined

interface Props { label?: string | undefined }

Omit the key instead of assigning undefined

1. Build the object without the key when there is no value rather than setting it to undefined

How to prevent it

• Decide per property whether a present-undefined is meaningful; omit keys you do not have rather than passing undefined.

Frequently asked questions

Related guides

References

• Node.js documentation
• npm CLI documentation
• GitHub Actions documentation