R help - Sep 2010 - using survexp and ratetable with coxph object that includes a factor term

Hello,

I'm attempting to use the ratetable argument to
survexp in the survival package.  I use
the example from the ?survexp help page below,
and then slightly modify it to produce an error.

library(survival)
data(pbc)

#fit a model without any factors

pfit1 <- coxph(Surv(time, status > 0) ~ trt + log(bili) +
          log(protime) + age + platelet, data=pbc)

#this works as expected

survexp(~ trt, ratetable = pfit1, data = pbc)

#now I fit a similar model, simply adding the 'sex' term
#note sex is now the only factor in the model

pfit2 <- coxph(Surv(time, status > 0) ~ trt + log(bili) +
          log(protime) + age + platelet + sex, data = pbc)

#however, I now get an error with survexp
survexp(~ trt, ratetable = pfit2, data = pbc)

Error in ratetable(trt = trt, bili = bili, protime = protime, age = age,
: object 'sexf' not found

Does anyone have any suggestions?

Thank you,
Erik Iverson

sessionInfo()
R version 2.11.1 (2010-05-31)
x86_64-unknown-linux-gnu

locale:
  [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
  [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
  [5] LC_MONETARY=C              LC_MESSAGES=en_US.UTF-8
  [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
  [9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] grDevices datasets  splines   graphics  utils     stats     methods
[8] base

other attached packages:
[1] Hmisc_3.7-0     survival_2.35-8

loaded via a namespace (and not attached):
[1] cluster_1.12.3 grid_2.11.1    lattice_0.18-8 tools_2.11.1