R devel - Feb 2009 - \usage without \alias

Hi the list,

I am checking a package and I get a warnings :

--- 8< ----
Objects in \usage without \alias in documentation object 'plot,Calinski'
--- 8< ----

'Calinski' is a S4 class and I define a S4 method for ploting it. Here 
is my plotCalinski.rd file :

--- 8< ----
\name{plot,Calinski}
\alias{plot,Calinski}
\alias{plot,Calinski-method}

\title{ ~ Function: plot for Calinski ~ }
\description{
  \code{plot} the Calinski creterion.
}
\usage{
plot(x, y, ...)
}
--- 8< ----

Any idea of what is wrong ?

Thanks
Christophe