Why doesn't this template class work inside another class?

I can do:

template <int n>
struct Buffer
{
    char buffer[n * 128];
};

template <int n>
Buffer<n> buffer; // When I instantiate this the compiler makes many different static variables


int main()
{
    buffer<sizeof(int)>;
    buffer<sizeof(char)>;
    buffer<sizeof(double)>;
    buffer<sizeof(std::string)>;
}

But for some reason it fails to compile when I want the buffer object inside a class as a static variable:

template <int n>
struct Buffer
{
    char buffer[n];
};

struct MyStaticClass
{
    template <int n>
    static inline Buffer<n> buffer;
};

int main()
{

    MyStaticClass::buffer < sizeof(int)>;
    //'public: static Buffer<4> MyStaticClass::buffer<4>': inline variable is undefined

}

I am on Visual 2019 Community 16.4.5 I have /std:c++latest flag on