stamen_watercolor doesn't work

Hi, I am working with get_stadiamap and I would like to have the "stamen_watercolor" maptype. However, I get this error with the basic usage :

bbox <- c(left = 24.61, bottom = 59.37, right = 24.94, top = 59.5)
get_stadiamap(bbox, zoom = 12, maptype = "stamen_watercolor") %>% ggmap()

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Error:
! Failed to evaluate glue component {filetype}
Caused by error:
! object 'filetype' not found
Backtrace:
1. ... %>% ggmap()
3. ggmap::get_stadiamap(bbox, zoom = 12, maptype = "stamen_watercolor")
4. base::lapply(...)
5. ggmap (local) FUN(X[[i]], ...)
6. ggmap:::get_stadiamap_tile(...)

All maptypes work except the stamen_watercolor. Any help with this would be highly appreciated :)

Thanks!
Coralie