alignment issue

It was suggested the following might be a bug. When I try to place the slope block with one of the legs turned upwards (in order to make an inverted roof corner) I can't make the tiles go in the correct direction. The alignment won't change with the tool in the c menu. Heres a screenshot where I've used all the three options for texture alignment and they still look the same: the tiles are facing one of the legs no matter what.