I am attempting to get restaurant details from the Google places API in R. I can successfully get the 20 results that Google provides however I realize that as it returns a next_page_token, then this means there are other results (which is logical is there are more than 20 restaurants around the 50km radius of the location I am searching). However when I use next_page_token it returns NULL. 
Here is my code:
install.packages("googleway")
library(googleway)
key <- 'my key'
df_places <- google_places(search_string = "restaurant", 
                       location = c(-33, 151),
                       page_token = "next_page_token",
                       radius = 50000,
                       key = key)
df_places$results$name
df_places$results$rating
df_places$results$formatted_address
df_places$results$geometry$location
And here is what it returns without next_page_token:
 [1] "Gennaro's Italian Restaurant"                   
 [2] "Mount Broke Wines & Restaurant"                 
 [3] "Oak Dairy Bar"                                  
 [4] "Bimbadgen"                                      
 [5] "Subway Restaurant"                              
 [6] "Muse Restaurant"                                
 [7] "Ocean Restaurant"                               
etc...
Here is what it returns with next_page_token:
> df_places$results$name
NULL
Just wondering what I am doing wrong to repeatedly return NULL?