All, I have a set up as shown below. ?Everything works fine but the new serialization default is 3, I would like it to serialize to version = 2. ?I've tried a couple of different ways to set version and googled around but so far I've had no luck. ?The package builds fine but then sets dependency to R(>= 3.5.0) this no backward compatibility. ?Actually, I don't mind this personally but is there a way with the below set-up to avoid this? Best, Glenn zzz.r file as below ???????.onAttach <- function(libname, pkgname){ ??????packageStartupMessage( ??????"Bond Lab is a registered trademark of Bond Lab Technologies.") ??????BondLabSetUp() ??????} A file in my inst directory with functions that I serialize on load an example of which is below. ?????????Scenario( ?????????Name = "NCs", ?????????Type = "Immediate", ?????????ShiftType = "Parallel", ?????????Shiftbps = "0", ?????????Formula = function(rates.data = vector(), Shiftbps = "character"){ ?????????yield.basis = 100 ?????????pmax(0.01, as.numeric(rates.data) + (as.numeric(Shiftbps)/yield.basis)) ?????????}) A .R file?BondLabSetUp.R #' Setup function for the R package BondLab to create the needed objects #' #' @export BondLabSetUp <- function(){ do.call(source, list(file = paste(system.file(package = "BondLab"), "/Scenario/Scenario_SpotCurve", sep = ""), local = TRUE))