ccxt: Bittrex fetchBalance() fails

Using a fresh API key pair:

const balance = await market.fetchBalance()

produces

bittrex https://bittrex.com/api/v1.1/account/getbalances?nonce=1501049737&apikey=[redacted] { method: 'GET',
  headers:
   { 'User-Agent': 'ccxt/1.1.83 (+https://github.com/kroitor/ccxt) Node.js/8.1.4 (JavaScript)',
     apisign: [redacted] },
  body: undefined }
(node:22773) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): TypeError: Cannot read property 'length' of undefined
(node:22773) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.