验证发回的信息body一直提示Hash must be a string or a buffer

[Wizhiai]

alipays.query({ outTradeId: '201807069324414819' }).then(function (ret) { console.log("***** ret.body=" + ret.body);

    //签名校验
    var ok = alipay.signVerify(ret.body);
    console.log(ok);
});

UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 2): TypeError: Hash must be a string or a buffer