Error: `defaultStyles[key] is not a function` when adding a custom key to `styles`

Good day.

I find it very convenient that I can place all the styles for Select component in the separate file and import them:

// index.js
import styles from './styles';

<Select
	styles={styles}
	// ...
/>

// styles.js
const styles = {
	control: (provided, state) => ({
		...provided,
		// Control custom styles 
	}),
};

However, I have a fair amount of custom components, and I want them to share the same API for styles that react-select has. For that, I create a custom key in the styles object like so:

const styles = {
	control: (provided, state) => ({
		...provided,
		// Control custom styles 
	}),
	checkbox: (provided, state) => ({
		...provided,
		// Checkbox custom styles 
	}),
};

But when I start using that key inside a component, I get this error:

Uncaught TypeError: defaultStyles[key] is not a function

I use it like so:

export const Checkbox = ({ isChecked, isDisabled, ...props }) => {
	const { children, className, cx, getStyles, innerProps } = props;

	return (
		<div
			css={getStyles('checkbox', props)}
			className={cx(
				{
					'checkbox': true,
				},
				className,
			)}
		>
			<IconCheckmark fill={isChecked ? 'white' : 'transparent'} css={{
				transition: transition,
			}}/>
		</div>
	);
};

The error is pointing to the line 1055 in the following code snippet:
https://github.com/JedWatson/react-select/blob/ec3bd2eb7f5b10fa6ce3f9cac9d811a46a74f42a/packages/react-select/src/Select.tsx#L1051-L1059

Seems like react-select doesn't expect custom keys in styles parameter.

I've read the docs, and especially the Styles - cx and custom Components section, but that doesn't help to solve the problem.

Is there another way of writing custom styles to match the react-select API?

Thanks in advance.

Start at packages/react-select/src/Select.tsx around lines 1051-1059 and reproduce the custom checkbox key used with getStyles. Compare that path with the Styles - cx and custom Components documentation; done means the documented styling API handles the reported custom component case without the TypeError.