rest warning

[raoul.megelas]

hi, everybody

I don't know how to avoid the following warnig.
Please can you tell me what is wrong or missing there?
Thanks
        raoul
        address@hidden


\score {
        \notes {
        \time 3/4 \clef G \key f \minor
        {
 R2 | \bar "||" 
    } 
   }
}

   ...
toto.ly:24:5: warning: barcheck failed at: 1/2:
 R2 |
      \bar "||" 
[3]
Preprocessing elements... 
Calculating column positions... 
paper output to `toto.tex'...