[R-pkg-devel] data and load version 3

I added two data sets (.rda) to my package eha, but when I build the new 
version I get:

 ?WARNING: Added dependency on R >= 3.5.0 because serialized objects in 
serialize/load version 3 cannot be read in older versions of R.? File(s) 
containing such objects: ?eha/data/swedeaths.rda?? ?eha/data/swepop.rda?

In DESCRIPTION I have 'Depends: R (>= 3.0.0)'

After googling for a while (found nothing relevant in 'WRE'), I 
understand that I have two options: (i) Change 'Depends' in DESCRIPTION 
as suggested, and (ii) using save with 'version = 2' for the new files.

And, if I am recommended to choose (i), should I recreate the old data 
files with 'version = 3'?

My guess is go for (i) and version = 3 for all data files, but I feel 
that I need advise.

Thanks, G?ran