problem using uniroot with integrate

Hi,

I'm trying to calculate the value of the variable, dp, below, in the
argument to the integral of dnorm(x-dp) * pnorm(x)^(m-1).  This
corresponds to the estimate of the sensitivity of an observer in an
m-alternative forced choice experiment, given the probability of
a correct response, Pc, a Gaussian assumption for the noise and
no bias.  The function that I wrote below gives me an error:

Error in f(x, ...) : recursive default argument reference

The problem seems to be at the statement using uniroot,
because the furntion est.dp works fine outside of the main function.
I've been using R for awhile but there are still many nuances
about the scoping and the use of environments that I'm weak on
and would like to understand better.  I would appreciate any
suggestions or solutions that anyone might offer for fixing
my error.  Thank you.

dprime.mAFC <- function(Pc, m) {
                est.dp <- function(dp, Pc = Pc, m = m) {

                  pr <- function(x, dpt = dp, m0 = m) {
                        dnorm(x - dpt) * pnorm(x)^(m0 - 1)
                            }

                  Pc - integrate(pr, lower = -Inf, upper = Inf,
                  dpt = dp, m0 = m)$value
                }

        dp.res <- uniroot(est.dp, interval = c(0,5), Pc = Pc, m = m)
        dp.res$root
        }