plotRGB error when calling plot_map() in rayshader package in R

Question

I'm trying to use the rayshader package in R to plot elevation data, but I'm getting an error when I call the plot_map() function. I can't even get the example to run without running into the following error. Any ideas on how to get this function to run?

error in evaluating the argument 'x' in selecting a method for function 'plotRGB': unused argument (asp = 1)

Here is the example code that I am calling.

library(rayshader)

#Here, I load a map with the raster package.
loadzip = tempfile() 
download.file("https://tylermw.com/data/dem_01.tif.zip", loadzip)
localtif = raster::raster(unzip(loadzip, "dem_01.tif"))
unlink(loadzip)

#And convert it to a matrix:
elmat = raster_to_matrix(localtif)

#We use another one of rayshader's built-in textures:
elmat %>%
  sphere_shade(texture = "desert") %>%
  plot_map()