no visible binding

Could someone advise me about how to react to the message:

* checking R code for possible problems ... NOTE
slm: no visible binding for global variable 'response'

from R CMD check SparseM    with
* using R version 2.6.0 Under development (unstable) (2007-09-03 r42749)

The offending code looks like this:

"slm" <-
function (formula,  data, weights, na.action, method = "csr",
     contrasts = NULL, ...)
{
     call <- match.call()
     m <- match.call(expand.dots = FALSE)
     m$method <- m$model <- m$x <- m$y <- m$contrasts <-  m$... <- NULL
     m[[1]] <- as.name("model.frame")
     m <- eval(m, sys.frame(sys.parent()))
     if (method == "model.frame")
         return(m)
     Terms <- attr(m, "terms")
     weights <- model.extract(m, weights)
     Y <- model.extract(m, response)
     X <- as.matrix.csr(model.matrix(Terms, m, contrasts))
     fit <- {
         if (length(weights))
             slm.wfit(X, Y,  weights, method, ...)
         else slm.fit(X, Y,  method, ...)
     }
     fit$terms <- Terms
     fit$call <- call
     attr(fit, "na.message") <- attr(m, "na.message")
     class(fit) <- c(if (is.matrix(Y)) "mslm", "slm")
     fit
}


url:    www.econ.uiuc.edu/~roger            Roger Koenker
email    rkoenker at uiuc.edu            Department of Economics
vox:     217-333-4558                University of Illinois
fax:       217-244-6678                Champaign, IL 61820