Issues downloading CHIRPS data in R

I'm trying to download monthly precipitation data from CHIRPS, but my code keeps throwing an error saying arguments imply differing number of rows. I even tried using the example query from the chirps documentation and I get the same error.

Example:

library(chirps)lonlat <- data.frame(lon = c(-55.0281,-54.9857),                     lat = c(-2.8094, -2.8756))dates <- c("2017-12-15", "2017-12-31")dt <- get_chirps(lonlat, dates)

Am I doing something wrong here?