句点必须是C++17计时库中比率的特化?

我显然太笨了,不能使用C++17 <chrono> 图书馆正在编译以下内容。。。

#include <chrono>
#include <iostream>

int main() {
    using clock = std::chrono::steady_clock;
    using duration = std::chrono::duration<double, std::chrono::seconds>;
    using timepoint = std::chrono::time_point<clock, duration>;
    timepoint t0 = clock::now();
    for (int i = 0; i < 1000; i++) {
        timepoint t = clock::now();
        duration d = t-t0;
        double seconds = d.count();
        std::cout << seconds << std::endl;
    }
}

我得到。。。

/usr/include/c++/8/chrono:319:16: error: static assertion failed:
                                  period must be a specialization of ratio
      static_assert(__is_ratio<_Period>::value,
                    ^~~~~~~~~~~~~~~~~~~

有什么想法吗?