React-dnd: Erreur non interceptée: l'élément doit être un objet

Salut. J'ai essayé de trouver des mentions de ce bogue, mais malheureusement rien n'était présent ici ou sur le web.

J'ai commencé un projet et j'ai une configuration assez simple et en essayant de faire glisser un élément, j'ai cette erreur:
http://prntscr.com/jpfale

Voici mon composant Drag:

import React from 'react';
import PropTypes from 'prop-types';
import styled from 'styled-components';
import { DragSource } from 'react-dnd';

const Container = styled.span`
  margin: 10px;
  font-size: 4rem;
  text-transform: uppercase;
  cursor: pointer;
  transition: 0.4s;

  &.is-clicked {
    color: ${({ theme }) => theme.colors.purple};
  }

  &.is-hidden {
    opacity: 0;
  }
`;

const spec = {
  beginDrag(props) {
    console.log('test');
    return {};
  },
};

const WordItem = ({
  children,
  item,
  isHidden,
  handleClick,
  connectDragSource,
}) => {
  return connectDragSource(
    <span>
      <Container
        className={item.clicked ? 'is-clicked' : isHidden}
        onClick={handleClick}
      >
        {children}
      </Container>
    </span>,
  );
};

WordItem.propTypes = {
  children: PropTypes.string.isRequired,
  item: PropTypes.objectOf(PropTypes.any).isRequired,
  isHidden: PropTypes.string.isRequired,
  handleClick: PropTypes.func.isRequired,
};

export default DragSource('word', spec, (connect, monitor) => ({
  connectDragSource: connect.dragSource(),
  isDragging: monitor.isDragging(),
  dropResult: monitor.getDropResult(),
  canDrag: monitor.canDrag(),
}))(WordItem);

Conteneur connecté au contexte:

export default DragDropContext(HTML5Backend)(App);

J'ai déjà fait un projet avec react-dnd, mais c'est la première fois que je vois ce problème. Voici mon package.json si ce problème peut être lié à la compatibilité des bibliothèques:

{
  "name": "",
  "version": "1.0.0",
  "description": "npm i -g prettier",
  "main": "index.js",
  "scripts": {
    "clean": "rimraf dist",
    "dev": "cross-env NODE_ENV=development node devServer.js",
    "build": "npm run clean && cross-env NODE_ENV=production webpack --config=webpack.build.config.js -p && node productionServer.js",
    "flow": "flow"
  },
  "author": "",
  "license": "ISC",
  "browserslist": [
    "last 5 versions",
    "not ie < 11"
  ],
  "prettier": {
    "singleQuote": true,
    "trailingComma": "all"
  },
  "dependencies": {
    "axios": "^0.18.0",
    "babel-plugin-styled-components": "^1.5.1",
    "es6-promise": "^4.2.4",
    "prop-types": "^15.6.1",
    "rc-slider": "^8.6.1",
    "react": "^16.3.2",
    "react-dnd": "^3.0.2",
    "react-dnd-html5-backend": "^3.0.2",
    "react-dom": "^16.3.2",
    "react-motion": "^0.5.2",
    "react-redux": "^5.0.7",
    "react-router-dom": "^4.2.2",
    "redux": "^4.0.0",
    "redux-thunk": "^2.2.0",
    "styled-components": "^3.2.6",
    "svg-inline-loader": "^0.8.0",
    "xml2js": "^0.4.19"
  },
  "devDependencies": {
    "autoprefixer": "^8.3.0",
    "babel-core": "^6.26.0",
    "babel-eslint": "^8.2.3",
    "babel-loader": "^7.1.4",
    "babel-plugin-transform-class-properties": "^6.24.1",
    "babel-plugin-transform-object-rest-spread": "^6.26.0",
    "babel-plugin-transform-runtime": "^6.23.0",
    "babel-preset-env": "^1.6.1",
    "babel-preset-flow": "^6.23.0",
    "babel-preset-react": "^6.24.1",
    "browserslist": "^3.2.4",
    "compression-webpack-plugin": "^1.1.11",
    "cross-env": "^5.1.4",
    "css-loader": "^0.28.11",
    "eslint": "^4.19.1",
    "eslint-config-airbnb": "^16.1.0",
    "eslint-config-prettier": "^2.9.0",
    "eslint-plugin-import": "^2.11.0",
    "eslint-plugin-jsx-a11y": "^6.0.3",
    "eslint-plugin-prettier": "^2.6.0",
    "eslint-plugin-react": "^7.7.0",
    "express": "^4.16.3",
    "extract-text-webpack-plugin": "^4.0.0-beta.0",
    "file-loader": "^1.1.11",
    "flow-bin": "^0.70.0",
    "html-webpack-plugin": "^3.2.0",
    "image-webpack-loader": "^4.2.0",
    "node-sass": "^4.8.3",
    "postcss-loader": "^2.1.4",
    "prettier-eslint": "^8.8.1",
    "react-hot-loader": "^4.0.0",
    "rimraf": "^2.6.2",
    "sass-loader": "^7.0.1",
    "style-loader": "^0.20.3",
    "url-loader": "^1.0.1",
    "webpack": "^4.6.0",
    "webpack-cli": "^2.1.2",
    "webpack-dev-middleware": "^3.1.2",
    "webpack-hot-middleware": "^2.22.1"
  }
}

Veuillez aider à résoudre ce problème.