Procced

code/modules/mob/living/carbon/human/species/shadow.dm

@@ -39,10 +39,10 @@
 /datum/action/innate/shadow/darkvision/Activate()
 	var/mob/living/carbon/human/H = owner
 	if(!H.vision_type)
-		H.vision_type = new /datum/vision_override/nightvision
+		H.set_sight(new /datum/vision_override/nightvision)
 		to_chat(H, "<span class='notice'>You adjust your vision to pierce the darkness.</span>")
 	else
-		H.vision_type = null
+		H.set_sight()
 		to_chat(H, "<span class='notice'>You adjust your vision to recognize the shadows.</span>")
 
 /datum/species/shadow/on_species_gain(mob/living/carbon/human/H)

code/modules/mob/mob.dm

@@ -1356,6 +1356,10 @@ GLOBAL_LIST_INIT(slot_equipment_priority, list( \
 	SEND_SIGNAL(src, COMSIG_MOB_UPDATE_SIGHT)
 	sync_lighting_plane_alpha()
 
+/mob/proc/set_sight(datum/vision_override/O)
+	vision_type = O
+	update_sight()
+
 /mob/proc/sync_lighting_plane_alpha()
 	if(hud_used)
 		var/obj/screen/plane_master/lighting/L = hud_used.plane_masters["[LIGHTING_PLANE]"]