Fret number does not match note

[marc]

Hi,

In the following score with staff and tab, the generated
fret index for the first "a8" that matches "a8\5" in the tab
is generated in the output as "fret 12 on the A string" and should
Be "fret 0".
If I put "a,8\5" in the tab the ouput is correct. But should the 
tab and score contain the same notes with the same octave ?

Thanks



Score is:
--------------------
\score  {
  \context StaffGroup <<
    \notes 
      \context Staff {
        \relative c
        \partial 2
           r8 a8 c8 <d a> 
           <d a>  <d a> c <bes f bes d>
        }
    \notes 
      \context TabStaff {
        \relative c
        \partial 2
           r8 a8\5 c8\5 <d\4 a\3>
           <d\4 a\3> <d\4 a\3> c <bes f bes d>
        }
  >>
}
--------------------
 
_______________________________
Marc