Warning message using writeRaster() - not updated for proj >= 6

Using the code below to write a raster to disk:

library('raster')
        
r <- raster(nrow = 5856, ncol = 9141)
r[] <- 1:ncell(r)
        
writeRaster(r, tempfile(fileext = ".tif"), overwrite = TRUE)

always produces a warning message:

In .gd_SetProject(object, ...) : NOT UPDATED FOR PROJ >= 6

What causes the message and how can I avoid it?