STL unordered_map crashes with __m128 values

I was tracking the error in using __m128 (SSE vector) as the value in std :: unordered_map. This causes a segmentation error at runtime using mingw32 g ++ 4.7.2.

See the example below. Is there a reason why this should fail? Or maybe a workaround? (I tried to wrap the value in the class, but that didn't help.) Thanks.

#include <unordered_map>
#include <xmmintrin.h>          // __m128
#include <iostream>

int main()
{
    std::unordered_map<int,__m128> m;
    std::cerr << "still ok\n";
    m[0] = __m128();
    std::cerr << "crash in previous statement\n";
    return 0;
}

Compilation settings: g ++ -march = native -std = C ++ 11