Cannot compile constexpr member function with GCC 4.9 [duplicate]

The following trivial code does not compile with GCC 4.9 and MSVC 2015:

struct A
{
    static constexpr size_t GetTextureCount()
    {
        return 5;
    }

    static constexpr size_t a = GetTextureCount();
};

GCC 4.9 error: 'static constexpr size_t ISparkleRenderer::GetTextureCount()' called in a constant expression

MSVC 2015 error C2131: expression did not evaluate to a constant

Why this code does not compile? Probably I need higher compiler versions?