Why is a unique_ptr not freed after a constructor calls an exception?

In the following code:

#include <memory>
#include <iostream>

void mydeallocator(int * x) {
    std::cerr << "Freeing memory" << std::endl;
    delete x;
}

struct Foo {
    std::unique_ptr <int,std::function <void(int*)>> x;
    Foo(bool fail) : x(new int(1),mydeallocator) {
        if(fail)
            throw;
    }
};

int main() {
    {auto foo1 = Foo(false);}
    {auto foo2 = Foo(true);}
}

It appears that memory is not being deallocated properly when Foo(true) is called. Namely, when we compile and run this program, we have the result:

Freeing memory
terminate called without an active exception
Aborted

I believe that the message Freeing memory should be called twice. Basically, according to this question, my understanding is that the stack should unwind on the constructor for Foo and that x should call its destructor, which should call mydeallocator. Certainly, this is not happening, so why is the memory not being freed?