Statusline's minwidth not respected?

[Lifepillar]

Vim gurus,
if I set the statusline as follows:

set statusline=X%1MX

the % item does not occupy any space if the buffer is unmodified,
despite the minimum width of one character. Is that expected behaviour?

What I would expect is what I get with:

set statusline=X%1(%M%)X

Thanks,
Life.