2 overloads have similar conversions (C++, templates)

Let's say I have following class template:

template<typename T>
class Foo
{
    int value;

public:
    int& operator() (int some_arg) { return value; }
    int operator() (T t) { return value; }
};

I use it like that:

int main()
{
    Foo<double> f;

    double x = 3;
    f(x);

    //...
}

I get compilation error 2 overloads have similar conversions which refers to calling: f(x).

1. Shouldn't I get such error only if I would pass int as template argument?

2. Is there a way to solve this issue but without replacing one of the operators with function or [] operator?