Why does g++5 deduces object instead of initializer_list in auto type deduction

I recently came upon this code:

struct Foo{};

int main() 
{
    Foo a;
    // clang++ deduces std::initializer_list
    // g++5.1 deduces Foo
    auto b{a}; 
    a = b;
}

It compiles fine with g++5.1, but fails in clang++. The reason is that clang++ deduces the type of b as std::initializer_list<Foo>, whereas g++5.1 deduces as Foo. AFAIK, the type should indeed be (counter-intuitive indeed) std::initializer_list here. Is this correct, and if yes, is this a known "bug" of g++5?