Expose_stan_functions not working after updating rstan and R

Can you test v2.26.7?

remove.packages(c("rstan", "StanHeaders"))
install.packages("StanHeaders", repos = c("https://mc-stan.org/r-packages/", getOption("repos")))
install.packages("rstan", repos = c("https://mc-stan.org/r-packages/", getOption("repos")))