variadic template of a specific type

I want a variadic template that simply accepts unsigned integers. However, I couldn't get the following to work.

struct Array
{
    template <typename... Sizes> // this works
    // template <unsigned... Sizes> -- this does not work (GCC 4.7.2)
    Array(Sizes... sizes)
    {
        // This causes narrowing conversion warning if signed int is supplied.
        unsigned args[] = { sizes... };
        // ...snipped...
    }
};

int main()
{
    Array arr(1, 1);
}

Any help appreciated.

EDIT: In case you're wondering, I'm trying to use variadic template to replicate the following.

struct Array
{
    Array(unsigned size1) { ... }
    Array(unsigned size1, unsigned size2) { ... }
    Array(unsigned size1, unsigned size2, unsigned size3) { ... }
    // ...
    Array(unsigned size1, unsigned size2, ..., unsigned sizeN) { ... }
};