survexp with weights

lines(survexp( ~ trt, ratetable=pfit.wtd, data=pbc), col='purple')

Error in eval(expr, envir, enclos) : object 'albumin' not found

  The code does work, however, using the latest version of survival.
(Use of case weights in survexp languished on my to-do list for a long
long time.)

Terry Therneau