Error in xtfrm.data.frame(x) : cannot xtfrm data frames when using ggadjustedcurves

[hhchang0210]

Steps to reproduce the problem

I have a dataset. The independent variable, statin, is a factor variable.
str(t1$statin)
Factor w/ 2 levels "1","2": 2 1 1 1 2 1 2 1 1 1

fit2 <- coxph( Surv(death_365days_duration,death_365days) ~ statin, data = t1 )
ggadjustedcurves(fit2, data = t1, method = "average", variable = "statin")

->Error in xtfrm.data.frame(x) : cannot xtfrm data frames

Or

fit2 <- coxph( Surv(death_365days_duration,death_365days) ~ strata(statin), data = t1 )
ggadjustedcurves(fit2, data = t1, method = "average", variable = "statin")

->Error in xtfrm.data.frame(x) : cannot xtfrm data frames

Could someone help me how to fix it?
Thank you.