get_currency_balance response incorrect

[iuouiyiuty]

用fibos.js时，调用get_currency_balance是正常的，
console.notice(client.getCurrencyBalanceSync("eosio.token", 'account', "FO@eosio"));

但是直接调rpc的时候，一样的参数，返回结果却是错误
curl -X POST -H "Content-Type: application/json" -d '{ "code":"eosio.token", "account": "account", "symbol":"FO@eosio"}' "http://my_rpc_url"

{
  "code": 500,
  "message": "Internal Service Error",
  "error": {
    "code": 3010014,
    "name": "symbol_type_exception",
    "what": "Invalid symbol",
    "details": [
      {
        "message": "precision 160 should be <= 18",
        "file": "symbol.hpp",
        "line_number": 141,
        "method": "reflector_init"
      },
      {
        "message": "error unpacking eosio::chain::symbol",
        "file": "raw.hpp",
        "line_number": 644,
        "method": "unpack"
      },
      {
        "message": "Error unpacking field sym",
        "file": "raw.hpp",
        "line_number": 367,
        "method": "operator()"
      },
      {
        "message": "error unpacking eosio::chain::asset",
        "file": "raw.hpp",
        "line_number": 644,
        "method": "unpack"
      }
    ]
  }
}

测试了一下，在eos上这样调用没有问题。
这种情况有解决办法吗？还是只能用get_table_rows来获取余额