I'm using a mod called better landfill so maybe that's the issue. The construction signaler was not picking up landfill ghosts for me. The other mod like this, construction combinator, does work for me with landfill ghosts, but I think the performance is lower with that mod so I was looking forward to using this one. Is landfill supposed to work?

Thanks

Whoops, it was not working with landfill or other tiles, I didn't realize they were a separate category of ghost. Fortunately it was an easy thing to add, I've just released version 0.16.2 which works with landfill and other tile ghosts.