virtual destructor 'default' = linker error

I think the following code should work:

// Base.h

class Base
{
public:
    Base() = default;
    virtual ~Base() = default;
};

// Derived.h

class Derived : public Base
{
public:
    Derived();
    ~Derived() override;
};

// Derived.cpp

Derived::Derived()
    : Base()
{
    // do some work
}

Derived::~Derived()
{
    // do some work
}

I get "unresolved external symbol" linker error for both the constructor and destructor of the base class. However if I change the = default to { }, everything works.

Am I missing something from the specification?

PS. I'm using VS2013.