biblatex suppression of label after year

Question

Possible Duplicate:
Suppressing em-dashs for recurrent authors and letter suffixes for years when using biblatex-chicago

I'm compiling my CV in latex using a slightly modified version of what provided in this link http://robjhyndman.com/research/cv.sty. For the list of publications I'm using bib latex with the following settings :

\usepackage[sorting=ynt,
            bibstyle=authoryear-comp,
            defernumbers=true,
            maxnames=300,
            firstinits=true,
            uniquename=init,
            backend=bibtex8,
            dashed=false,
            arxiv=abs
]{biblatex}

I've some publications which are quite similar (for examples two contributions in the same conferences). Let's say the following two

@Misc{vianello:meetinga09,
author = {Vianello, N and Doe, J and Smith, W},
title =      {First title},
howpublished = {presented at the meeting A},
year =   {2009}
}

@Misc{vianello:meetingb09,
author = {Vianello, N and Brown, D and Gates, B},
title =      {Second title},
howpublished = {presented at the meeting A},
year =   {2009}
}

When I include them in the CV unfortunately (the insertion is done through a \nocite{*} command) the two contribution appears as

N. Vianello, J. Doe and W. Smith (2009) First title, presented at the meeting A
N. Vianello, D. Brown and B. Gates (2009b) Second title, presented at the meeting A

with an annoying (2009b) in the second year. How can I avoid it?