jonestetc already explained the gist of it - combineReducers expects vanilla javascript objects, not Immutable ones; you can find an example Immutable-compatibl

jonestetc already explained the gist of it - combineReducers expects vanilla javascript objects, not Immutable ones; you can find an example Immutable-compatible implementation here: https://github.com/gajus/redux-immutable https://github.com/gajus/redux-immutable We don't use it though, it's really easy to just create your own version and use that and preferred to have one less dependency.