C++ Linker Error With Class static constexpr

I am compiling the following simple program with g++-4.6.1 --std=c++0x:

#include <algorithm>

struct S
{
    static constexpr int X = 10;
};

int main()
{
    return std::min(S::X, 0);
};

I get the following linker error:

/tmp/ccBj7UBt.o: In function `main':
scratch.cpp:(.text+0x17): undefined reference to `S::X'
collect2: ld returned 1 exit status

I realize that inline-defined static members do not have symbols defined, but I was under the (probably flawed) impression that using constexpr told the compiler to always treat the symbol as an expression; so, the compiler would know that it is not legal to pass a reference to the symbol S::X (for the same reason you can't take a reference to the literal 10).

However if S is declared as namespace, i.e. "namespace S" instead of "struct S", everything links fine.

Is this a g++ bug or do I still have to use a trick to workaround this annoyance?