# react-dnd-unmounted-set-state
If you quickly drag "<drag handle>" past the red markers of the neighboring `<Letter />`, the child `<Side />` component will unmount before collect runs. That will lead to the following error.
```
index.js:1 Warning: Can't perform a React state update on an unmounted component. This is a no-op, but it indicates a memory leak in your application. To fix, cancel all subscriptions and asynchronous tasks in a useEffect cleanup function.
in Side (at Letter.tsx:33)
console.<computed> @ index.js:1
r @ backend.js:6
warningWithoutStack @ react-dom.development.js:530
warnAboutUpdateOnUnmountedFiberInDEV @ react-dom.development.js:25738
scheduleUpdateOnFiber @ react-dom.development.js:23679
dispatchAction @ react-dom.development.js:17076
(anonymous) @ useCollector.js:31
handleChange @ DragDropMonitorImpl.js:44
dispatch @ redux.js:222
(anonymous) @ DragDropManagerImpl.js:93
HTML5Backend.handleTopDragEnter @ HTML5Backend.js:230
```