The following is with `eslint-plugin-react@6.10.3`. If a propType is quoted for some reason like this: ```js MyComponent.propTypes = { 'data-id': PropTypes.string, }; ``` Then the `require-default-props` rule gives the following warning: ``` propType "undefined" is not required, but has no corresponding defaultProp declaration. ``` Howwever, giving the propType a default value like this does satisfy the rule: ```js MyComponent.defaultProps = { 'data-id': 'test', }; ``` It seems like this is an issue with the formatting of the error message.