taglib. Flac file cover?

Question

C++ / C#

You need to get the cover from the audio file. I use Taglib (version 1.8). Problems arise with flac .
As far as I understand, the best option to extract cover is this:

founded = extractFlac(file);

        if(!founded)
        {
            TagLib::ID3v2::Tag* tag = file->ID3v2Tag();
            if(tag)
                founded  = extractId3(tag);
        }

extractFlac

bool extractFlac(TagLib::FLAC::File* file)
{
    const TagLib::List<TagLib::FLAC::Picture*> picList = file->pictureList();
    if(!picList.isEmpty())
    {
        // Let's grab the first image
        TagLib::FLAC::Picture* pic = picList[0];
        return saveData(pic->data());
    }

    return false;
}

extractId3

bool extractId3(TagLib::ID3v2::Tag* tag)
{
    const TagLib::ID3v2::FrameList& frameList = tag->frameList("APIC");
    if(!frameList.isEmpty())
    {
        // Grab the first image
        TagLib::ID3v2::AttachedPictureFrame* frame =
            static_cast<TagLib::ID3v2::AttachedPictureFrame*>(frameList.front());
        return saveData(frame->picture());
    }

    return false;
}

The problem is that

const TagLib::List<TagLib::FLAC::Picture*> picList = file->pictureList();

picList is always empty and ID3v2 is missing.
I looked in the bug tracker of the project - it seems like there is no such bug (Windows 7, 32-bit)
or, if this is not a bug, tell me how to correctly extract cover.
Thanks in advance