C++ unique_ptr and map

I'm trying to use the C++0x unique_ptr class inside a map like so:

// compile with `g++ main.cpp -std=gnu++0x`

#include <string.h>    
#include <map>
#include <memory>

using namespace std;

struct Foo {
    char *str;    
    Foo(char const *str_): str(strdup(str_)) {}
};

int main(void) {
    typedef std::map<int, unique_ptr<Foo>> Bar;
    Bar bar;
    auto a = bar.insert(Bar::value_type(1, new Foo("one")));
    return 0;
}

However GCC gives me the following error (shortened, I think this is the relevant part, please test on your own C++ compiler):

main.cpp:19:   instantiated from here
/usr/include/c++/4.4/bits/unique_ptr.h:214: error: deleted function ‘std::unique_ptr::unique_ptr(const std::unique_ptr&) [with _Tp = Foo, _Tp_Deleter = std::default_delete]’
/usr/include/c++/4.4/bits/stl_pair.h:68: error: used here

I'm really not sure what I've done wrong, this works on MSVC. I have found very similar questions, that seem alike, however their solutions do not work for me.

matt@stanley:/media/data/src/c++0x-test$ gcc --version
gcc-4.4.real (Ubuntu 4.4.3-4ubuntu5) 4.4.3