unique_ptr to a derived class as an argument to a function that takes a unique_ptr to a base class

I'm trying to use a unique_ptr to derived class in a function that takes a unique_ptr to a base class. Something like:

class Base {};

class Derived : public Base {};

void f(unique_ptr<Base> const &base) {}

…

unique_ptr<Derived> derived = unique_ptr<Derived>(new Derived);
f(derived);

If I understand this answer correctly, this code should work, but it causes the following compile errors:

error C2664: 'f' : cannot convert parameter 1 from 'std::unique_ptr<_Ty>' to 'const std::unique_ptr<_Ty> &'

IntelliSense: no suitable user-defined conversion from "std::unique_ptr<Derived, std::default_delete<Derived>>" to "const std::unique_ptr<Base, std::default_delete<Base>>" exists

If I change f to take unique_ptr<Derived> const &derived, it works fine, but that's not what I want.

Am I doing something wrong? What can I do to work around this?

I'm using Visual Studio 2012.