Erro no Chrome ao executar 'add' da 'IDBObjectStore'

Bom dia,

estou recebendo um erro ao testar meu NegociacaoDao.js no Chrome (versão 66.0.3359.181), porém funciona normalmente no Firefox!

Comando:

ConnectionFactory.getConnection().then(connection => new NegociacaoDao(connection).adiciona(new Negociacao(new Date(), 7, 100)));

Erro:

Uncaught (in promise) DOMException: Failed to execute 'add' on 'IDBObjectStore': The object store uses out-of-line keys and has no key generator and the key parameter was not provided.
    at Promise (http://localhost:3000/js/app/dao/NegociacaoDao.js:16:18)
    at new Promise (<anonymous>)
    at NegociacaoDao.adiciona (http://localhost:3000/js/app/dao/NegociacaoDao.js:11:16)
    at ConnectionFactory.getConnection.then.connection (<anonymous>:1:84)

NegociacaoDao.js:

class NegociacaoDao {

    constructor(connection) {

        this._connection = connection;
        this._store = 'negociacoes';
    }

    adiciona(negociacao) {

        return new Promise((resolve, reject) => {

            let request = this._connection
                .transaction([this._store],'readwrite')
                .objectStore(this._store)
                .add(negociacao);

            request.onsuccess = evento => {

                resolve();
            };
            request.onerror = evento => {

                console.log(evento.target.error);
                reject('nao foi possivel adicionar a negociacao');
            };
        });
    }
}