Including files from parent dir

There's something I don't understand about @include:

Say, I have:

    doc/foo.texi
    doc/gpl.texi
    bar.texi

if my `foo.texi` has

    @include gpl.texi
    @include ../bar.texi

I will be able to use successfully both

    cd doc; makeinfo --no-split foo.texi -o ../foo.info

will work fine, but

    makeinfo --no-split doc/foo.texi -o foo.info

will signal an error that it can't find `../bar.texi`
(note: it *did* find `gpl.texi`).

Why are the two includes treated differently?
How can I convince `makeinfo` to find the `bar.texi` file in both cases?


        Stefan