# 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 ```