Add `RasterLayer` to `addLayersControl` in leaflet

I have to RasterLayer-objects (raster1 and raster2) in R. And I want to add them both to a leaflet-map. I also wanted to have the option to show or hide them. So I thought I'd add them with their names to the addLayersControl-option. But it doesn't work. It shows both layers at the same time and I can't hide them. So far my code looks like this. I think the problem is in how to add them to the addLayersControl-function.

leaflet() %>%
  addTiles() %>%
  addRasterImage(raster1, opacity = 0.3) %>% 
  addRasterImage(raster2, opacity = 0.3) %>% 
  addLayersControl(
    baseGroups = c("OSM (default)"),
    overlayGroups = c("raster1", "raster2"),
    options = layersControlOptions(collapsed = FALSE)
  )

I guess that's kind of easy,but I can't think of any sollution.