Do non-local C++11 lambdas live in anonymous namespaces?

A recent build of GCC 4.8 gives the following code, when in a header file:

auto L = [](){};

struct S
{
    decltype(L) m;
};

the following warning:

test.hpp:3:8: warning: 'S' has a field 'S::m' whose type uses the anonymous namespace [enabled by default]
 struct S
        ^

Why does the compiler consider the type of the lambda to use the anonymous namespace? I made the lambda global, I didn't use an anonymous namespace anywhere.

UPDATE: The compiles gives the same warning even if I put the lambda in an explicit namespace, like so:

namespace N
{
    auto L = [](){};
}

struct S
{
    decltype(N::L) m;
};

UPDATE 2: In fact, it seems even class scope lambdas have the same problem:

class N
{
    static constexpr auto L = [](){};
};

struct S
{
    decltype(N::L) m;
};