Redux-Thunk: function.then is not a function

1

I get this error with the below code

TypeError: dispatch(...).then is not a function
(anonymous function)
src/actions.js:35

 32 | // }; 
 33 |   
 34 | export const updateStateData = (stateData, stateVariable) => (
dispatch => {
> 35 |   return dispatch({ 
 36 |     type : 'stateUpdate', 
 37 |     payload : { 
 38 |       stateVariable,

export const updateStateData = (stateData, stateVariable) => (dispatch => {
  return dispatch({
    type : 'stateUpdate',
    payload : {
      stateVariable,
      stateData
    }
  })
    .then((returnedValue) => {
      console.log(returnedValue);
    })
});

Yet the below function, also with a chained .then() works. It seems the same to me. Anyone know what the difference is?

export const testThunk = () => ((dispatch) => {
  const fakeFetch = () => new Promise((resolve, reject) => (
    setTimeout(() => resolve('into the 1st promise data local, and then into the payload value of the action'), 2000)
  ));
  
  return fakeFetch()
    .then((resolvedValue) => {
      dispatch({
      type: 'thunkTest',
      payload: resolvedValue });
      
      return '1st promise return';
    })
    .then((returnedValue => {
      console.log('getstate call', store.getState());
      console.log(returnedValue);
    }))
  });