Raster package update led to error

Earlier, I succesfully created spatial maps using raster version 3.5.2.
The same code couldn't be run with the package update with version 3.5.15.
The error occured at

proj4string(P) <- CRS("+init=epsg:28992")

with an error code

Error in CRS("+init=epsg:28992") : NA
Your suggestions will be appreciated.

Thank you