diff --git a/code/modules/mob/mob_planes.dm b/code/modules/mob/mob_planes.dm
index 947619a2b28..9e4952ba269 100644
--- a/code/modules/mob/mob_planes.dm
+++ b/code/modules/mob/mob_planes.dm
@@ -7,6 +7,7 @@
 	var/list/plane_masters[VIS_COUNT]
 
 /datum/plane_holder/New(mob/this_guy)
+	ASSERT(ismob(this_guy))
 	my_mob = this_guy
 
 	//It'd be nice to lazy init these but some of them are important to just EXIST. Like without ghost planemaster, you can see ghosts. Go figure.