force natural sign

[lfanele]

hi,
is there a way to put a natural sign manually? in this example the  
natural sign is left out at the b, but i want to make sure the reader  
understands it is a b not a bes.

natural_accidental.pdf
Description: Adobe PDF document

This is the code for the example:

\version "2.6.3"

\layout    {
    \context
        {\Staff
            \remove Time_signature_engraver
            \remove Bar_engraver
}
}

\header
{tagline = " "}

{
\context Staff  #(set-accidental-style 'modern)
\clef treble
f g a bes c' d' e' f' g' a' b' c'' d'' e'' fis'' g''
}

Thanks a lot!
Stephen