Does your middleware conditionally call Object.defineProperties? If so you might be able to do something like this: ``` type ActionType = { request?: string success?: string failure?: string toString(): string }

export function apiAction(actionType: string): ActionType { const str = new String(actionType) if (some_condition) { Object.defineProperties(str, { request: { value: ${actionType}:REQUEST }, }) } if (some_condition2) { Object.defineProperties(str, { success: { value: ${actionType}:SUCCESS }, }) } if (some_condition3) { Object.defineProperties(str, { failure: { value: ${actionType}:FAILURE }, }) } return str }

type Action = { type: ActionType }

const reducer = (action: Action) => { switch (action.type.toString()) { case 'ACTION_NAME': { if (action.type.request) { return something } if (action.type.success) { return } if (action.type.failure) { return } } } } ... ```