{includeblock} affects $_l->extends

@layout.latte

<!doctype>
{include #content}

menu.latte

{block #menu /}

default.latte

{layout @layout.latte}

{? dump($_l->extends)} prints @layout.latte
{includeblock menu.latte}
{? dump($_l->extends)} prints NULL

{block #content /}

Is this a bug or a feature?