reduxjs/redux · error · Error

Actions may not have an undefined "type" property. You may…

Error message

Actions may not have an undefined "type" property. You may have misspelled an action type string constant.

What it means

Even when the action is a plain object, Redux requires a `type` property that is defined. Actions with no type, or with type: undefined, cannot be routed by reducers or recorded by devtools, so dispatch rejects them. This usually indicates a misspelled constant that resolved to undefined.

Solutions

1. Inspect the action object right before dispatch: confirm `action.type` is a defined string.
2. Check the import for the action-type constant: `import { ADD_TODO } from './types'` and ensure ADD_TODO is exported.
3. Beware circular imports: move shared constants to a leaf module that no one cycles back from.
4. Use a linter rule (e.g. eslint-plugin-redux) to flag undefined action types.

Example fix

// before (types.ts exports ADD_TODO, but you imported a typo)
import { ADD_TODO } from './types'        // undefined: not exported
dispatch({ type: ADD_TODO, payload: x })

// after
import { ADD_TODO } from './types'
dispatch({ type: ADD_TODO, payload: x })

if (typeof action.type === 'undefined') {
  throw new Error(`Action is missing a defined type: ${JSON.stringify(action)}`)
}
store.dispatch(action)

const hasDefinedType = (a): a is { type: unknown } =>
  a !== null && typeof a === 'object' && typeof (a as any).type !== 'undefined'

When it happens

Trigger: dispatch({ type: ADD_TODO }) where ADD_TODO is undefined (misspelled or not exported); dispatch({ payload: x }) with no type field at all; action built from a constants object whose key was renamed; reducer/action file using a string literal that got tree-shaken to undefined.

Common situations: Renaming an action-type constant in one file but not the action creator; circular import that makes the constant undefined at dispatch time; copy-paste that omits `type:`; destructuring that yields undefined for the type value.

Related errors

• Action "type" property must be a string. Instead, the…
• Actions must be plain objects. Instead, the actual type was
• Reducers may not dispatch actions.
• Dispatching while constructing your middleware is not…
• Expected the enhancer to be a function. Instead, received

AI-assisted analysis of reduxjs/redux@3084fc33bb (2026-08-12). Data as JSON: /api/errors/ba7ee13ca7768f18. Report an issue: GitHub.

Appendix: source

Thrown at src/createStore.ts:280

   * a `type` property which may not be `undefined`. It is a good idea to use
   * string constants for action types.
   *
   * @returns For convenience, the same action object you dispatched.
   *
   * Note that, if you use a custom middleware, it may wrap `dispatch()` to
   * return something else (for example, a Promise you can await).
   */
  function dispatch(action: A) {
    if (!isPlainObject(action)) {
      throw new Error(
        `Actions must be plain objects. Instead, the actual type was: '${kindOf(
          action
        )}'. You may need to add middleware to your store setup to handle dispatching other values, such as 'redux-thunk' to handle dispatching functions. See https://redux.js.org/tutorials/fundamentals/part-4-store#middleware and https://redux.js.org/tutorials/fundamentals/part-6-async-logic#using-the-redux-thunk-middleware for examples.`
      )
    }

    if (typeof action.type === 'undefined') {
      throw new Error(
        'Actions may not have an undefined "type" property. You may have misspelled an action type string constant.'
      )
    }

    if (typeof action.type !== 'string') {
      throw new Error(
        `Action "type" property must be a string. Instead, the actual type was: '${kindOf(
          action.type
        )}'. Value was: '${String(action.type)}' (stringified)`
      )
    }

    if (isDispatching) {
      throw new Error('Reducers may not dispatch actions.')
    }

    try {
      isDispatching = true

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