R convert sf object back to SpatialPolygonsDataFrame

I used

 as(nc, 'Spatial')

as part 2 of the vignette by Edzer Pebesma indicated (Scroll to the bottom of the page).

I had to use sf:::as_Spatial() as workaround.

library(sf)
nc <- st_read(system.file("shape/nc.shp", package="sf"))

# sf -> sp
nc_sp <- as_Spatial(nc$geom)      # Error: could not find function "as_Spatial"

nc_sp <- sf:::as_Spatial(nc$geom) # This works

library(sp)
plot(nc_sp)