Brace-enclosed initializer list works for constructor but not for make_unique

Question

I am struggling to understand why make_unique<T> does not accept a Brace-enclosed initializer list, when the constructor of T works fine with them.

I am using SFML and creating an instance of RenderWindow. RenderWindow takes a VideoMode instance as its first parameter. The constructor for VideoMode takes 3 arguments (the last one optional) and I was successfully able to pass a braced-initializer in its place:

sf::RenderWindow window({w_width, w_height}, title);

I later tried to create a unique_ptr using make_unique. The standard says that the arguments to make_unique are forwarded to the constructor of the template parameter so I thought the following should work:

auto window = std::make_unique<RenderWindow>({w_width, w_height}, title);

But unfortunately, I get the following compiler error using GCC 5.1.1.

error: no matching function for call to ‘make_unique(<brace-enclosed initializer list>, const char* const&)’
 auto window_ptr = std::make_unique<sf::RenderWindow>({w_width, w_height}, title);

I guess I've miss-understood the subtleties make_unique, but I couldn't find a clear answer as why the make_unique code above doesn't work.

Please can someone shed some light on this for me?

Cheers